The Sapirstein method was used to study the circulatory conditions of hypophysectomized rats treated with oestrogen and with vasopressin. It was found that in rats hypophysectomized for several weeks there are decreases in the blood pressure, cardiac output, renal fraction of the cardiac output and the renal blood flow. 1 hr after vasopressin injection following a 10-day oestrone pretreatment, the renal fraction of the cardiac output and the renal blood flow decreases significantly compared to the hypophysectomized untreated group, and the renal vascular resistance increases to a considerable extent. The vasoconstriction can also be detected in the kidneys of oestrone-pretreated hypophysectomized animals, following the administration of vasopressin. The protective effect of hypophysectomy against renal cortical necrosis induced by hormone treatment is therefore not exerted by means of the inhibition of the renal vasospasm. It may be presumed that after the hypophysectomy the O2 demand of the kidneys decreases and so the kidneys better endure the O2 deficiency caused by the renal vasospasm.
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