Discrepancy between aldosterone production and renin-angiotensin system activity in Brattleboro rats

It was demonstrated before that in addition to their typical changes in water-sodium-potassium balance Brattleboro rats, homozygous for hypothalamic diabetes insipidus (DI), revealed a discrepancy between aldosterone level and plasma renin activity (PRA). In the present study PRA was significantly increased (79%), and concomitantly juxtaglomerular (JG) index was increased, reflecting an increased secretory activity of renin-producing JG cells. Plasma concentration of aldosterone was significantly lower (-36%) in DI rats than in their Long Evans (LE) controls. Adrenal blood flow rates were not significantly different in both groups of rats but aldosterone concentrations in the adrenal venous effluents were significantly lower (-66%) in DI rats than in LE rats, suggesting that in vivo production rate of aldosterone was reduced in DI rats. This assumption was confirmed by morphometric data of zona glomerulosa. Our results demonstrated a significant reduction (50%) of angiotensin II receptors in the adrenal glands of DI rats, referring to the number of binding sites and to Kd. This finding threw light on the dissociation between a decreased aldosterone production and stimulated renin-angiotensin system in DI rats.