Water and electrolyte balance in adrenalectomized rats with diabetes insipidus (Brattleboro strain) given antidiuretic hormone

Vasopressin [antidiuretic hormone (ADH) as pitressin tannate in oil] was injected daily into male Brattleboro rats with hypothalamic diabetes insipidus before and after adrenalectomy. Body weight increased after ADH treatment. Urine volume, water intake, and excretion of osmotically free water fell as urinary osmolarity increased; all stabilized after 5–6 days. Total solute, sodium, calcium, and magnesium excretory rates also diminished. After adrenalectomy, body weight, food and water intakes, and urine volumes were reduced compared with those of sham-operated ADH-injected animals. The proportion of the dietary intakes of sodium, potassium, calcium, magnesium, and chloride appearing in the urine all increased initially after adrenalectomy. Seven days after operation, plasma sodium concentration and muscle sodium content were reduced; plasma potassium concentration and muscle water content were also higher than in sham-operated animals. The pattern of adrenal insufficiency observed in these ADH-injected rats was similar to that previously found in adrenalectomized normal, but not diabetic, rats. Vasopressin clearly influeces some of the characteristic features of adrenalectomized animals.