Glomerular epithelial cell changes after ischemia or dehydration. Possible role of angiotensin II

Glomerular visceral epithelial cells (podocytes) undergo flattening and spreading of major processes detectable by scanning electron microscopy in early postischemic acute renal failure in both animals and man. The authors examined the kinetics of development of these epithelial cell changes in the renal pedicle-clamping model of ischemic renal failure in the rabbit. They found that these changes develop progressively, increasing with increasing length of ischemia, and occur while the pedicle clamp is still in place. To assess the possible role of angiotensin II and vasopressin in producing the epithelial changes, the authors compared glomerular morphology before and during pedicle clamping in hydrated rabbits and in dehydrated rabbits. Dehydration alone produced changes in glomerular epithelial cells comparable to those seen in the postischemic kidney. The angiotensin-converting enzyme inhibitor captopril did not prevent the podocyte changes in either group. In vitro incubation studies confirmed that both angiotensin II and vasopressin produce glomerular epithelial cell changes with a threshold between 10(-7) M and 10(-8) M, a concentration that may be physiologically significant for angiotensin II, which is synthesized at the glomerulus and may have local paracrine effects. Such local synthesis may not be inhibited by systemic administration of captopril. Angiotensin II may play a role in producing podocyte alterations during renal ischemia, as well as in the dehydrated state.