Abstract

A study has been made of the effects of pituitrin, pitressin and pitocin when injected in therapeutic doses into man. Pituitrin and pitressin produce for a brief period a fall in pulse rate, oxygen consumption and cardiac output which is succeeded by a more prolonged rise in these functions. Pitocin causes only a slight increase in the oxygen consumption and negligible changes in the circulation. The decreased cardiac output after pituitrin and pitressin injections is attributed to a reflex initiated by the threatened increase in blood pressure which would result from the constriction of cutaneous vessels. The subsequent elevation in the cardiac output and pulse rate is due to the accumulation of catabolites during the period of decreased oxygen consumption after pituitrin and pitressin. This accumulation of catabolites brings about a condition of "oxygen debt" the removal of which is manifested in a later increased oxygen consumption. The marked pressor effect of pituitary extracts observed in animals under certain anesthetics is not observed in normal man in the doses used in this study.