WATER METABOLISM IN THE HYPOPHYSECTOMIZED BRATTLEBORO (DI) RAT

ABSTRACT To re-examine the relative roles of the anterior and posterior pituitary hormones in diabetes insipidus, the effects of hypophysectomy and hormone replacement therapy in hereditary diabetes insipidus rats (Brattleboro strain) was compared with effect of similar treatment of rats without diabetes insipidus. In agreement with experiments on surgically induced diabetes insipidus, hypophysectomy sharply reduced water intake in rats with hereditary diabetes insipidus (DI rats). Water intake remained considerably higher, however, in these rats than in the non-DI rats following hypophysectomy. ADH treatment reduced water intake nearly to levels seen in non-DI rats. In water deprivation studies it was found that urine concentrating ability of the hypophysectomized non-DI rats was almost twice that of the hypophysectomized DI rats. None of the hormones tested restored water turnover of the hypophysectomized DI rats to that seen in sham operated controls. ACTH and T3 increased water intake, but not to levels seen in DI rats with intact pituitary glands. These experiments lead us to concur with those who hold that maximal flow in diabetes insipidus requires the participation of the anterior pituitary hormones. In addition these experiments indicate that ADH or ADH like material is physiologically functional in hypophysectomized rats (other than the Brattleboro strain), and that its presence accounts for the absence of diabetes insipidus following pituitary removal.