Muscle-stimulating fatty acid isolated from placenta

¹ Department of Veterinary Science, College of Agriculture, University of Osaka Prefecture, Osaka, Japan

A smooth-muscle-stimulating fatty acid has been isolated from the human placenta. The neutralization value, iodine value and results obtained from alkali-isomerization, biological assay and paper chromatography provided evidence indicating that the active substance is eicosatetraenoic acid (arachidonic acid). The active fraction manifested the following biological properties: a) delayed-slow-contracting action on the isolated intestine and uterus, which seemed to be a direct one on muscle fibers; b) hypotensive action on rabbit blood pressure in a dose of 5 µEq. The evidence considered in relation to the literature on smooth-muscle-activating, lipid-soluble acids, strongly indicates that eicosatetraenoic acid is more active than the previously studied fatty acids, and among the most active lipid-soluble smooth-muscle-activating substances.