Ultrastructure of the proximal convoluted tubules during repair following hormonally induced necrosis in rat kidney

Summary

The proximal convoluted tubules of rats were examined electron microscopically at various intervals (1, 2 and 3 days, 1, 2, 4 and 6 weeks) after focal cortical necrosis was induced by a single injection of posterior pituitary extract after pretreatment with oestrogen for 10 days. Epithelial regeneration seemed to originate within the zone of necrosis from low residual cells having a simple structure. Th3se dedifferentiated by 24 hours, resulting in cells of embryonic nature that were very rich in ribosomes but had almost no other organelles. Most organelles appeared generally on the 3rd day. Relining of the tubules and later gradual maturation of these cells often led to complete reestablishment of cellular ultrastructure in 6 weeks. At the same time parts of the tubules remained lined by an epithelium of incomplete maturation. The lack of adequate regeneration and the grade of the basement membrane damage roughly parallelled each other. Thus it is assumed, that severe damage of the basement membrane inhibits adequate regeneration, although the reverse effect cannot be ruled out. Nevertheless, a poor regeneration resulting in a conduction tube with presumably limited other functions seems to be possible even when injury of the basement membrane is severe, provided that no disruption has occured.