Action of cobra venom on the renal cortical tissues: electron microscopic studies

the effect of intramuscular (im) injection of a sub-lethal dose of naja haje cobra venom (0.015 mg/gm body weight) on the ultrastructure of renal cortical tissues of rabbits was studied at different time intervals after envenomation. succinic dehydrogenase (sdh) enzyme activity was also detected in the renal cortical tubules. three hours after venom injection, slight changes were seen in visceral cells and glomerular endothelia. the cortical tubular epithelia revealed an increase of lysosomal structures, cytoplasmic vacuolization, and nuclear irregularity. severe ultrastructural changes were recorded 6 hours after envenomation, including hypertrophied parietal cells, blebbed visceral epithelial cells, and foot process disorganization. dilated glomerular capillaries lined by hypertrophied endothelial cells and signs of mesangiolysis were also observed. the proximal tubular epithelia showed vesiculated endoplasmic reticulum and numerous lysosomal vacuoles, while the distal tubular epithelia were mostly necrotic. these alterations were more intense 12 hours after venom injection. parietal and visceral cells showed similar changes to those of the six-hour group. most of the glomerular endothelial cells lost their integrity and diffused into the capillary lumen. mesangiolysis was also observed. the proximal tubular epithelial cells revealed severely affected cellular organelles, dilated brush borders, disruption of the basal membrane infoldings, and cellular necrosis. the distal tubular epithelia lost most of their cytoplasmic electron density and cellular organelles. necrotic cells were also seen. generalized mitochondrial alterations were observed in all renal cortical cell types accompanied by a marked depletion of sdh enzymatic activity in those cells. it is believed that these venom-induced non-specific lesions could be due to secondary synergistic action of more than one venom toxin, which mainly target the mitochondria in all components of renal cortical tissues.