STUDIES OF THE ANTIDIURETIC ACTIVITY OF BLOOD AND HYPOTHALAMUS OF HYPOPHYSECTOMIZED RATS

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Abstract
The hypothalami of animals with diabetes insipidus tended to have somewhat lower levels of antidiuretic activity than were present in animals hypophysectomized for the same length of time. Serum of intact rats, fasted but hydrated ad libitum, contains antidiuretic activity of between 50 to 400 microunit equivalents of vasopressin/ml of serum. Serum of recently hypophysectomized rats contains much less antidiuretic activity. Serum of animals hypophysectomized for 30 days or longer contains only slightly less antidiuretic activity than is found in serum of intact animals. Serum of animals with diabetes insipidus contained very little antidiuretic activity. Posterior pituitaries of intact, fasted but ad libitum hydrated rats, contain from 10,000 to greater than 200,000 microunit equivalents of vasopressin. Hypothalami of recently hypophysectomized animals contain less antidiuretic activity than those of intact animals, values being from 500 to 10,000 microunit equivalents of vasopressin. Hypothalami of animals hypophysectomized for 30 days and fasted but hydrated ad libitum contained essentially the same amount of antidiuretic activity as was present in hypothalami of intact animals. Hydration increased the antidiuretic content and dehydration decreased it.