In order to determine whether or not
antidiuretic hormone (ADH) is essential to the inhibition of an acute water diuresis in
adrenal insufficiency, the response to oral water loads was tested in rats with hereditary hypothalamic
diabetes insipidus (DI) which lack ADH. It was found that 60 min after water loads of 3 or 5% of
body weight urine flow was significantly lower and urine osmolality significantly higher in adrenalectomized DI rats than in the same DI rats before removal of their adrenal glands. The efficacy of gluco- and
mineralocorticoids in reversing the inhibition was then determined in the same adrenalectomized DI rats.
Prednisolone alone, administered either acutely or chronically, restored the response in urine flow to that seen in the same rats before
adrenalectomy, but failed to correct the defect in urinary dilution.
Aldosterone when given alone tended to correct the diluting ability but not the response in urine flow. When these two adrenal cortical
hormones were given simultaneously, both the urine flow and urine osmolality were nearly identical to what they had been in the same DI rats before
adrenalectomy. These studies strongly suggest (a) that ADH is not essential to the inhibition of an acute water diuresis in
adrenal insufficiency, although it may abet the inhibition in individuals without
diabetes insipidus, which can elaborate ADH; and (b) that both gluco- and
mineralocorticoids are required in
adrenal insufficiency in order to fully restore the water diuresis as judged by the dual criteria of urine flow and urine osmolality.