Zona glomerulosa morphology and function in streptozotocin-induced diabetic rats

Streptozotocin-induced diabetic rats showed a significant lowering in both PRA (-31%) and basal plasma aldosterone concentration (-59%), coupled with a notable atrophy of the zona glomerulosa (-30%) and its parenchymal cells (-36%). Kalaemia and the blood level of ACTH were not affected. Insulin infusion reversed all the streptozotocin-evoked effects. Analogous, though less conspicuous, changes were induced by experimental diabetes also in rats whose hypothalamo-hypophyseal-adrenal axis and renin-angiotensin system had been pharmacologically interrupted by the simultaneous administration of dexamethasone-captopril and maintenance doses of ACTH-angiotensin II: the drops in the basal plasma aldosterone concentration and in the volume of zona glomerulosa and its cells ranged from -20% to -22%. In these animals, experimental diabetes significantly depressed the aldosterone response to the acute stimulation with angiotensin II (-55%), potassium (-50%), and ACTH (-43%). These findings indicate that the well known impairment of renin release may only partially account for the antiadrenoglomerulotrophic effect of experimental diabetes in rats. The hypothesis is advanced that the chronic lack of insulin may directly depress both the growth of the zona glomerulosa and the newly synthesis of some enzymes of aldosterone synthesis.