Abstract
Summary
1) A hypotensive, smooth muscle-contracting principle has been identified in the placenta of the rabbit and of several other species. It is dialysable, stable to heat at neutral pH for 3 minutes at 100°C, and unstable in alkali and acid. It has been separated chromatographically and by use of inhibitors from acetyl choline, serotonin, and histamine. The active principle is hydrolysable with liberation of free amino acids and with resulting loss of activity on guinea pig ileum and blood pressure. It has been tentatively identified as a polypeptide. 2) On intravenous injection the active principle causes a fall in blood pressure, cardiac dilatation, intestinal and uterine peristalsis, and death from respiratory failure. It is found predominantly in the fetal part of the placenta and at all stages of pregnancy in the rabbit from 16th day to term.
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