Water-electrolyte balance and hypothalamo-pituitary-adrenocortical function in rats with inherited diabetes insipidus (Brattleboro strain).

Brattleboro rats, homozygous for hypothalamic diabetes insipidus (DI), compared to their Long Evans (LE) controls, revealed typical changes in water-sodium-potassium balance: hypernatremia and hyperosmolality and hypokalemia. Plasma renin activity was significantly increased (79%) and plasma concentration of aldosterone was significantly lower (--36%) in DI rats than in LE rats. Concomitantly aldosterone excretion in DI rats was increased sevenfold. Adrenal blood flow rates were not statistically different in both groups of rats but the aldosterone concentrations in the adrenal venous effluent were significantly lower (--66%) in DI rats than in LE rats, suggesting that the in vivo production rate of aldosterone was reduced in DI rats. Plasma concentration of ACTH was significantly decreased (by 25%) in DI rats. The reasons for the dissociation between the changes of aldosterone production and the variations of renin-angiotensin system activity were discussed.