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Saudi Journal of Kidney Diseases and Transplantation
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Table of Contents   
ORIGINAL ARTICLE  
Year : 2017  |  Volume : 28  |  Issue : 4  |  Page : 725-736
Apoptosis of rat renal cells by organophosphate pesticide, quinalphos: Ultrastructural study


Department of Pathology, Electron Microscopy Unit, Faculty of Medicine, King Khalid University, Abha, Saudi Arabia

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Date of Web Publication21-Jul-2017
 

   Abstract 


Quinalphos or Ekalux, an organophosphate pesticide, is used in controlling the pests of a variety of crops. Quinalphos was studied on male Sprague-Dawley albino rats. The acute po LD50 of technical Ekalux was 19.95 mg/kg in males. Ekalux, produced several pathological changes in the kidney. A glomerulus demonstrated capillary lumina occluded by degenerated cellular debris. Basement membrane showed irregular wrinkling and branching. The proximal tubular cells showed damage such as dilation of endoplasmic reticulum, accumulation of glycogen granules, and pyknotic nucleus. The changes also included swelling of the mitochondria and reduction of the cristae up to total destruction. The distal tubular changes included electron lucency and vacuolation of cytoplasm. The distal convoluted tubule wall showed edematous epithelial cells, formation of blebs, and microvilli loss. These results suggest that subchronic exposure of rats to Ekalux causes ultrastructural changes in renal corpuscle and marked ultrastructural changes in proximal and distal tubules.

How to cite this article:
Eid RA. Apoptosis of rat renal cells by organophosphate pesticide, quinalphos: Ultrastructural study. Saudi J Kidney Dis Transpl 2017;28:725-36

How to cite this URL:
Eid RA. Apoptosis of rat renal cells by organophosphate pesticide, quinalphos: Ultrastructural study. Saudi J Kidney Dis Transpl [serial online] 2017 [cited 2017 Sep 24];28:725-36. Available from: http://www.sjkdt.org/text.asp?2017/28/4/725/211330



   Introduction Top


Today, we live in a world heavily burdened by environmental toxins. Since the World War II industrial boom, our planet has become home to dangerous levels of persistent organic pollutants, which are toxins made up of organic chemicals and synthetics. These pollutants are almost everywhere - our soil, food, water, air, and our bodies.

Quinalphos or Ekalux, [O-O-diethyl-O-(quinoxalinyl-(2)-thionophosphate)] is an agro-chemical used by farmers to control the insects. It is effective against many insects and used also for controlling biting and sucking pests on vegetables and rice. Ekalux is widely used as agricultural insecticide.[1]

Several authors have studied the effects of various organophosphorous compounds on animals and humans. The effects of sublethal doses of quinalphos were evaluated in adult male rats for changes in testicular morphology, circulatory concentrations of hormones.[2] They irreversibly inhibit acetylcholinesterase production. The accumulation of acetylcholine in the muscarinic and nicotinic synapses causes over stimulation of neurotransmission in both the central and the peripheral nervous systems.[1],[3] Pesticides and their metabolites are excreted mainly by the kidneys.[4] The toxic effect of the insecticide abamectin on oxygen consumption and some biochemical characteristics (total protein, carbohydrate, and cholesterol in liver, muscle, kidney, and gills) of the tilapia fish (Oreochromis niloticus) had been estimated.[5] Suicidal or accidental overdose of organophosphorus can result in acute tubular necrosis.[6] In this study, we evaluated the effects of Ekalux on the kidney were evaluated on the basis of ultrastructural changes.


   Materials and Methods Top


One hundred male Sprague-Dawley albino rats, approximately five months and weighing 150–170 g, were used in the present study. The animals were housed in metal hygienic cages and maintained under constant air flow and suitable temperature during the whole period of the experiment. Rats were fed on a standard laboratory diet and water.

Out of the hundred animals, 40 were given quinalphos orally in the doses (10, 20, 30, 40, 50, 60, 70, and 80 mg/kg/body weight) to estimate the LD50. The LD50 was calculated according to Spearman’s formula (1975). The acute po LD50 of Ekalux has been reported as 19.95 mg/kg in males. Male rats were found to be more susceptible to Ekalux than female rats in the subchronic toxicity studies based on mortality, enzyme profiles, and cholinesterase inhibition.[7]

The remaining sixty animals were divided into four groups of fifteen animals each. The first group was kept as control while the remaining three groups represented the treated animals. The latter three groups were given the Ekalux insecticide daily by a single oral dose of 1/20, 1/30, and 1/40 LD50 for ten consecutive days.

After the above-mentioned periods of treatment, animals were sacrificed by cervical decapitation. Then, the animals were rapidly dissected, the kidney from control and treated groups were immediately excised, cut into small pieces, and directly fixed in 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer, pH 7.2, for two hours at 4°C, postfixed in 1% osmium tetroxide, dehydrated in an ascending series of ethanol, and embedded in Spurr’s resin through propylene oxide. Thin sections were stained with uranyl acetate and lead citrate and examined in a Jeol 1200 EX TEM at 80 KV.

The protocol for this research project has been approved by King Khalid University within which the work was undertaken and that it conforms to the provisions of the Declaration of Helsinki in 1995 (as revised in Edinburgh 2000).


   Results Top


In normal glomeruli, the visceral epithelial cells, or podocytes, have foot processes that are intact in normal glomeruli. The glomerular basement membrane (Bm) has three ultrastructural zones: the lamina densa in the middle, the lamina lucida (rara) externa, and the lamina lucida (rara) interna. The urinary space and the foot processes are at the top. Slit pore diaphragms connect the epithelial cell foot processes. The pores through the endothelial cell (En) are below the Bm. The endothelial cell nucleus sits over the origin of the mesangium [Figure 1]a.
Figure 1: Ultrastructure of normal rat kidney.
(a) A glomerulus showing some capillary lumina basement membranes, endothelial cells, mesangial matrix, visceral epithelial cells of podocytes and a part of Bowman’s capsule (arrow) lined by parietal epithelium (×8650). Insert: Higher magnification displaying the three layers of the glomerular basement membrane; an inner layer (the lamina rara interna, (i), an outer layer (the lamina rara externa, (e), and a dense central layer (the lamina densa, (d), thin diaphragms (arrow) and multiple finestrae (arrow head). (f), foot processes, cl, capillary lumen. (×37500). (b) A proximal convoluted tubule showing epithelial podocytes cells resting on the basement membrane and containing numerous mitochondria (m), few lysosomes (L), Golgi apparatus (Go), and a round nucleus (N). The apical surface of the epithelial cell containing long microvilli to form the bruch border and intercellular space (arrow) (×8000). (c) A distal convoluted tubule showing some epithelial cells (Ep) resting on the basement membrane, short microvilli (arrows), a round nucleus (N), mitochondria (m), endoplasmic reticulum (double arrows), and intercellular space (Thick arrow). Lu, lumen (×7500).


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The cells of the proximal convoluted tubule are cuboidal, with microvilli on their luminal side, lots of mitochondria, lateral margins very interdigitated, and an infolded membrane on their bottoms. There are canaliculi at the bases of the microvilli, with their tips pinching off to produce pinocytotic vesicles. These vesicles then fuse with lysosomes [Figure 1]b.

The distal convoluted tubule is lined by a simple cuboidal epithelium whose cells have several characteristic features. The apical end of each distal tubule cell does not have a brush border although there may be scattered microvilli. The apical ends of distal tubule cells tend to be more distinct than those of proximal tubule cells, conferring the usual appearance of a larger, clearer lumen in each distal tubule. Distal tubule cells have a high proportion of mitochondria in their cytoplasm. The plasma membranes of adjacent distal tubule cells are extensively interdigitated. As a consequence of such interdigitated cell membranes, boundaries between adjacent distal tubule cells are inconspicuous [Figure 1]c.

[Figure 2]a shows a glomerulus demonstrating some glomerular capillary lumina (cl) occluded by degenerated cellular debris at low doses of Ekalux 1/40 LD50. Narrowing of the glomerular capillary lumen was noted at doses 1/30 LD50 [Figure 2]b. While at the higher doses 1/20 LD50 of Ekalux, glomerulus was found to be enlarged and hypertrophied [Figure 2]c.
Figure 2: Ultrastructure changes of the glomeruli.
(a) A glomerulus demonstrating some glomerular capillary lumina (cl) occluded by degenerated cellular debris (stars), hypertrophied endothelial cells, and irregular wrinkling basement membrane (arrows). 1/40 LD50 (×7500). (b) A glomerulus showing narrowed glomerular capillary lumina (cl) and branched basement membrane. 1/30 LD50 (×6000). (C) Photomicrograph of a glomerulus showing enlarged and occluded capillary lumina (cl) by destructed or damaged endothelial cells and degenerated cellular debris (stars). Degenerated visceral epithelial cells (Ep) with lipid droplets are also seen. 1/20 LD50 (×4000). (d) A glomerulus showing degeneration of hypertrophied epithelial (Ep) and endothelial cells 1/30 LD50 (×6824).


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Bm showed irregular wrinkling at dose 1/40 LD50 of Ekalux. Branching of the Bm was observed at higher doses 1/30 LD50 [Figure 2]a and [Figure 2]b.

Ens showed enlargement and hypertrophy [Figure 2]a even at low doses of Ekalux 1/40 LD50. The amount of damaged and destructed

Ens and degenerated cellular debris were quite pronouced at high doses 1/20 LD50 [Figure 2]c. Degenerated visceral epithelial cells with lipid droplets were also seen at doses 1/30 and 1/20 LD50 of Ekalux [Figure 2]c and [Figure 2]d.

Damaged and necrotic epithelial cells with pyknotic nucleus were clearly seen in kidney exposed to Ekalux toxicity even at low doses 1/40 LD50 [Figure 3]a, Glomerulus displayed two hump-like deposition in the Bm of the glomerular capillary at doses 1/30 LD50 of treated groups [Figure 3]b. Damaged glomerulus showed escaped mitochondria, lysosomes, erythrocytes, and ghost bodies in the urinary space of the glomerulus in the treated groups of high doses of Ekalux [Figure 3]c. Same high doses of Ekalux also lead to damaged and hypertrophied parietal epithelial cells of the Bowman’s capsule. A renal corpuscle showed disappearance of Bowman’s capsule and also some degenerated tubular epithelial cell organelles such as mitochondria while the nuclei were observed in the urinary space by high doses of Ekalux 1/20 LD50 [Figure 3]d.
Figure 3: Changes of glomerular structures.
(a) A renal corpuscle showing focal branching basement membrane, necrotic epithelial cell (Ep) with pyknotic nucleus (N), and damaged epithelial cells (star), Cl, Capillary lumen.1/40 LD50 (×8333). (b) A glomerulus displaying two hump-like deposits (Hd) in the basement membrane of the glomerular capillary. Cl, lumina of glomerular capillary, 1/30 LD50 (×17500). (c) Photomicrograph of damaged glomerulus showing mitochondria (m), lysosomes (L), erythrocytes (R), and ghost bodies (stars) in the urinary space (u) of the glomerulus. Note the damaged and hypertrophied parietal epithelial cell on the Bowman’s capsule (arrow), Cl, capillary lumina, 1/20 LD50 (×8500). (d) A renal corpuscle showing disappearance of Bowman’s capsule (arrow) and some degenerated tubular epithelial cell organelles (star) such as mitochondria, nuclei observed in the urinary space (×4000).


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The proximal tubular cells showed marked ultrastructural changes in the epithelial cells of the nephron segment after Ekalux-intoxication. The cells showed damage such as dilation of endoplasmic reticulum (ER), accumulation of glycogen granules, and pyknotic nucleus even among the low-dose Ekalux-treated groups [Figure 4]a. In addition, at low doses of Ekalux 1/40 LD50, we observed an increase of micronuclei, formation of myelin figures and swelling of the Golgi complex [Figure 4]a.
Figure 4: Ultrastructural changes of both proximal and distal tubules as well as interstitium and arterioles.
(a) A proximal tubule showing light and dark degenerated epithelial cells (Ep). Damaged mitochondria and six pyknotic nuclei (N) are scattered in no limited necrotic epithelial cells. 1/40 LD50 (×3429). (b) A proximal tubule showing extremely degeneration of epithelial cells (Ep). 1/30 LD50 (×2000). (c) A group of erythrocytes (R) observed in the degenerated cytoplasm of epithelial cells (Ep). 1/20 LD50 (×5727). (d) A distal tubule illustrating edematous epithelial cells (Ep) which led to the formation of blebs and disappearing microvilli (arrows). 1/30 LD50 (×6000). (e) A micrograph showing interstitial hemorrhage (R) and extensive free organelles such as mitochondria (star) from the districted tubular epithelium. Note two neutrophils (Ne). 1/20 LD50 (×6000). (f) A micrograph showing an arteriole occluded with hypertrophied endothelial cells, focal vacuolizations (V), and mild damage of smooth muscle (SMC) microfibrils. A vacuole (star) is observed inside the nucleus (N) of smooth muscle. 1/40 LD50 (×4500).


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The changes included also swelling of the mitochondria and reduction of the cristae up to the total destruction of these mitochondria at doses 1/40 and increased at 1/30 LD50 of Ekalux [Figure 4]a and [Figure 4]b. Mitochondrial swelling within tubule cells of treated animals showed a marked dose-response relationship. Increased numbers of dense, granular lysosomes were observed in tubule cells of rats receiving Ekalux. Tubule cells displayed proteinaceous vacuoles with dense crystalloid structures, and cellular degeneration in low and medium doses of Ekalux [Figure 4]a and [Figure 4]b.

Microvillar loss of the proximal tubules noted in animal group treated by 1/30 LD50 of Ekalux [Figure 4]b.

There were also ultrastructural changes in renal tubular epithelial cells as capillary endothelial cell swelling or destruction that led to escape of erythrocytes into the degenerated epithelial cell cytoplasm with high doses of Ekalux [Figure 4]c.

The distal tubular changes included electron lucency and vacuolation of cytoplasm. The distal convoluted tubule wall showed edematous epithelial cells which led to the formation of blebs and microvilli loss at medium doses of Ekalux toxicity [Figure 4]d.

Destructed tubular epithelium was noted in animal group treated with 1/20 LD50 of Ekalux. Interstitial hemorrhages with free cellular organelles outside the cells were marked. Abundant mitochondria, as well as occasional mitochondrial swelling, were also noted [Figure 4]e.

Arterioles were showing a lot of changes by Ekalux at low doses of toxicity. Ens were hypertrophied with focal vacuolizations. Smooth muscles of arterioles showed damaged microfibrils. Nucleus also showed changes such as vacuoles inside the nucleus [Figure 4]e


   Discussion Top


Quinalphos or Ekalux [O-O-diethyl-O-(quinoxalinyl-(2)-thionophosphate)] is used worldwide in agriculture. The easy availability of these materials in developing countries leads to accidental and suicidal poisoning.[1] The ingestion of an organophosphorus is the most common route in cases of suicide attempts.

The analytical setup of Russo et al[8] for different samples of human tissues exposed to organophosphorus pesticides revealed that the lowest concentrations have been determined in healthy kidney samples. Quinalphos at a dose of 14 mg/kg body weight in male wistar rats for 15 days produced a reversible type of liver and kidney necrosis.[9]

Glomeruli

Glomeruli are highly specialized filtration barriers between the blood and urinary space. The filter has a number of unique characteristics that provide the essential properties for this renal filtration process and include highly specialized glomerular visceral epithelial cells (podocytes), a fenestrated glomerular capillary endothelial system, and intervening glomerular Bm (GBM) that is produced by both the podocytes and the endothelial cells.[10],[11] The exact location of the filtration barrier of the glomerular capillary wall, which consists of the endothelium, a basement membrane and a visceral epithelium, has not yet been determined. Rostgaard[12] suggested that the fenestral plugs are the primary site of the glomerular filtration barrier. This filtration barrier is the target of injury and ultimate scarring in a wide variety of kidney diseases.[13],[14]

In this study, we demonstrated some glomerular cl gets occluded by degenerated cellular debris as a direct effect of Ekalux at low doses. The GBM does not completely enclose the lumen, unlike the endothelial basement membrane in most vessels, but rather splays out over the mesangium to become the paramesangial Bm. This leaves a functional gap where materials from the capillary lumen or subendothelial zone can directly enter the mesangium without traversing the Bm. This explains why the mesangium is a preferential sequestration point for some types of debris, including immune complexes.[15]

Renal Ens showed irregular foot processes and thickening of the GBM. Narrowing of the glomerular capillary lumen was noted at doses 1/30 LD50. While at the higher doses of Ekalux, a glomerulus was found to be enlarged and hypertrophied.

Bm showed irregular wrinkling at low doses Ekalux. Branching of the Bm or hump-like deposition in the Bm was observed at medium doses. No changes in GBM thickness or width of podocyte pedicels noted in the kidneys of Peking ducks exposed to various combinations of methyl mercury chloride, lead acetate, and cadmium chloride.[16] Renal corpuscles of kidney after mercuric chloride toxicity and subsequent interaction with an organophosphate insecticide in birds revealed minor ultrastructural changes as vacuolation, swollen mitochondria of podocytes, and slight thickening of the GBM.[17] While, in cockerels exposed to cadmium chloride and subsequent interaction with an organophosphorus compound (methyl chlorfenvinphos) renal corpuscles showed irregular foot processes and thickening of the glomerular basement membrane.[17] The ultrastructural changes caused by B. moojeni venom in rat renal glomeruli included mesangiolysis, glomerular microaneurysms, and GBM abnormalities. In addition, there was a reduction in the number and width of podocyte pedicels, which caused a reduction in the number of filtration slits.[18]

We demonstrated that Ens were enlarged and hypertrophied even at low doses of Ekalux. At high doses, damaged and destructed Ens and degenerated cellular debris were marked. Degenerated visceral epithelial cells with lipid droplets were also seen. Damaged and necrotic epithelial cells with pyknotic nucleus were cleared in kidney exposed to Ekalux toxicity even at low doses. High doses of Ekalux lead to damaged and hypertrophied parietal epithelial cells of the Bowman’s capsule. Damaged glomerulus showed escaped of nuclei, mitochondria, lysosomes, erythrocytes and ghost bodies in the urinary space of the glomerulus at high doses of Ekalux-treated groups.

The changes described for the effects of Narthecium ossifragum on goat kidneys were endothelial damage and shortening and swelling of the foot processes. Peritubular capillaries had breaks in the vessel walls and irregular En edema, and the interstitium had marked edema.[19] The glomerular capillary wall of the kidney exposed to ethanol showed En swelling, apoptotic podocytes, and Bm thickening.[20]

These morphological changes were attributed to biochemical and physiological disturbances in the components of the GBM and mesangial matrix as well as in cytoskeleton-associated proteins of podocytic processes and could account for the breakdown of optimal glomerular filtration barrier functioning.

The proximal tubule

The proximal tubular cells showed damage such as dilation of ER, accumulation of glycogen granules, and pyknotic nucleus even at low doses of Ekalux-treated groups. In addition, at low doses of Ekalux 1/40 LD50, we observed increased of micronuclei, formation of myelin figures, and swelling of the ER and the golgi complex. We also noted swelling of the mitochondria and reduction of the cristae up to the total destruction of these mitochondria at low doses of toxicity. Mitochondrial swelling within tubule cells of treated animals showed a marked dose-response relationship. Increased numbers of dense, granular lysosomes were observed in tubule cells of rats receiving Ekalux. The results showed that intoxication induces an increase of lysosomal activity related to the shape, distribution as well as different degrees of the organelle condensation. Lysosomes play an important role in cellular pathology.[21] The disruption of lysosomes, with the consequent release of their contents may led to the damage produced in such cells. Lysosomes release cathepsins that are endowed with the capacity of triggering mitochondrial membrane permeability.[22]

Tubule cells displayed proteinaceous vacuoles with dense crystalloid structures and cellular degeneration in low and medium doses of Ekalux. Microvillar loss of the proximal tubules was noted in animal group treated by Ekalux.

These changes were also described when treated the rats by cyclosporine A.[23] They also described fibrillar deposits in podocytes and basolateral membrane dilatations in proximal tubules. Interstitial fibrosis and atrophy were also noted in addition to reduce glomerular and mesangial volume with basement membrane thickness.

The proximal tubules in the kidneys of Peking ducks exposed to various combinations of methylmercury chloride, lead acetate, and cadmium chloride showed some microvillar loss and an increase in the number and size of lipid droplets, vacuoles, and lysosomal bodies.[16] Proximal tubular cells after mercuric chloride toxicity and subsequent interaction with an organophosphate insecticide in birds[24] revealed nearly the same results observed in this study.

There was also capillary En swelling or destruction that led to escape of erythrocytes into the degenerated epithelial cell cytoplasm with high doses of Ekalux. Same results were noted in cadmium nephropathy.[25]

In the present study, severe degenerative changes were evident in nuclei and nucleoli. The nuclei were markedly damaged. Ekalux induced micronuclei in the hepatic cells with dilated envelope as we proved in the previous study. Abnormal condensation of nuclear chromatin and nuclear fragmentations were noted. Single intraperitoneal injection of Ekalux produced karyorrhexis and karyolysis in the hepatic nuclei of the Indian desert gerbil, Meriones hurriane (Jerdon).[26]

Susin et al[27] mentioned that apoptosis-inducing factor (AIF) resides in the mitochondrial intermembrane space. On induction of apoptosis, AIF translocates from the mitochondria to the nucleus and causes chromatin condensation and DNA fragmentation. Nuclear DNA damage and ligation of plasma-membrane death receptors have been recognized as initial triggers of apoptosis that induce mitochondrial membrane permeabilization and/or the direct activation of caspases.[22]

The distal tubule

The distal tubular changes included electron lucency and degenerative vacuolation of cytoplasm in addition to abundant mitochondria as well as mitochondrial swelling. These changes were observed in medium doses of Ekalux toxicity. We noted also ballooned mitochondria with cristae derangement, mitochondrial cristolysis, and abnormally shaped rough ER (RER).

The responses to sublethal doses in both smooth and RER were unusually enlarged, dilated, vesiculated, and increased in number. These vesicles appear to have formed from the dilated parts of RER by fragmentation or separation. Effects were most evident within cisternae of the RER, thus suggesting modifications of protein metabolism. Misfolding of proteins constitutes a fundamental threat to all living cells. The risk of protein misfolding is particularly acute in the ER. Accumulation of misfolded proteins in the ER would detrimentally affect the function and/or localization of the approximately one-third of all cellular proteins that translocate into the ER after synthesis on membrane-bound ribosomes.[28] Genetic analysis of the cellular adaptation to malfolded proteins in the ER has revealed a new signaling pathway initiated by the activation of IRE1, an ER-resident protein kinase and endonuclease. Recently, mammalian IRE1 homologues have been identified, and their response to ER stress is regulated by binding to the ER chaperone BiP. Mammalian IRE1s activate an alternative ER-stress signaling pathway mediated by the transcription factor ATF6.[29]

ER, lysosomes, and the Golgi apparatus are major points of integration of proapoptotic signaling or damage sensing. Each organelle possesses sensors that detect specific alterations, locally activates signal transduction pathways and emits signals that ensure interorganellar cross-talk.[22] The ER senses local stress through chaperones, Ca2+-binding proteins and Ca2+ release chan-nels, which might transmit ER Ca2+ responses to mitochondria. The ER also contains several Bcl-2-binding proteins, and Bcl-2 has been reported to exert part of its cytoprotective effect within the ER.[22] Kaufman[30] reported that, the ER is sensitive to alterations in homeostasis, where, on a variety of different stimuli, signals are transduced from the ER to the cytoplasm and the nucleus to eventually result in adaptation for survival or induction of apoptosis.

The golgi apparatus constitutes a privileged site for the generation of the proapoptotic mediator ganglioside GD3, facilitates local caspase-2 activation and might serve as a storage organelle for latent death receptors. Intriguingly, most organelle-specific death responses finally lead to either mitochondrial membrane permeabilization or caspase activation, both of which might function as central integrators of the death pathway.[22]

Another drastic pathological changes encountered in the present work were represented by the severe lesions in the mitochondria. The mitochondria appeared enlarged, swollen, and elongated with cristae derangement. The mitochondria were closed to the nucleus. This study demonstrates that the Ekalux induce mitochondrial toxicity in rat renal cells. With observations reported recently,[31] the same ultrastructural changes were seen in cells injected with inhibitory saccharomyces cerevisiae Dnm1 protein antibodies. The increase in mitochondrial volume was a necessary cellular adaptation to meet the heightened energy demands by the smooth endoplasmic reticulum to produce the necessary enzymes to detoxify the harmful toxins.[32]

The role of mitochondria in mammalian cell apoptosis is complex. Biochemical studies identified several mitochondrial proteins that can activate cellular apoptotic programs directly.[27],[33],[34],[35],[36] These proteins reside in the intermembrane space of mitochondria. In response to a variety of apoptotic stimuli, they are released to the cytosol and/or the nucleus. They promote apoptosis either by activating caspases and nucleases or by neutralizing cytosolic inhibitors of this process.[37] Apoptosis can proceed in the absence of caspase activity when the mitochondria are damaged.[37] The mitochondrial damage may also passively lead to cell death due to the loss of mitochondrial function.

Genotoxicity, inhibition of protein synthesis, and other cytotoxicity probably arising from processes such as alkylation of nucleic acids and/or alkylation and phosphorylation of proteins have been demonstrated in mammals after exposure to organophosphorus.[38],[39],[40]

Aspartate aminotransferase and alanine aminotransferase increased significantly in kidney. The increasing level of these enzymes may be an adaptive mechanism due to the stress of the toxicant.[41] Some of the toxic effects produced in mammals by insecticidal treatment are most probably arising from an influence of the insecticide on the respiratory chain, uncoupling of oxidative phosphorylation and ATPase activity.[9]

Organophosphorus induces H2O2 production and lipid peroxidation in a kidney cell line.6 Others have provided additional evidence for the occurrence of Organophosphorus-induced oxidative tissue damage evidenced by DNA-strand breaks,[40] increased activities of antioxidant enzymes,[42],[43] and down-regulation of glutathione peroxidase activity and glutathione.[44],[45] Lipid peroxidation, ATP depletion, DNA damage, protein oxidation, and intracellular calcium increase due to membrane permeability lesions may be the pathway for renal cell damage by organophosphorus.[6]

Destructed tubular epithelium was damaged with high doses of Ekalux. Interstitial hemorrhages with free cellular organelles outside the cells were marked. The distal convoluted tubule wall showed edematous epithelial cells which led to the formation of blebs and microvilli loss at medium doses of Ekalux toxicity. Organophosphorus-induced oxidative stress at the tubular level may play a role in the pathogenesis of acute tubular necrosis.[6] Arterioles showed a lot of changes by Ekalux at low doses of toxicity. Ens were hypertrophied with focal vacuolizations. Smooth muscles of arterioles showed damaged microfibrils. Nucleus also showed changes such as vacuoles inside the nucleus. The effects of Ekalux cause extreme damage to all renal cells.

Collectively, our electron micrographs of subchronic exposure of rats to Ekalux support the conclusion that the insecticides induced oxidative stress may play a role in the pathogenesis necrosis of glomeruli and acute tubular necrosis, involving both proximal and distal tubules.

Conflict of interest: None declared.



 
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Correspondence Address:
Refaat A Eid
Department of Pathology, Electron Microscope Unit, College of Medicine, King Khalid University, P. O. Box 641, Abha
Saudi Arabia
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