Effects of the medium chain octanoic fatty acid on the contractile activity of vascular smooth muscle tissues.

Multiple elevation of the octanoic fatty acid level in human sera is often observed in some hepatic diseases which are accompanied by cardiovascular disorders, hypotension, and increased cardiac stroke volume. Different experiments reveal the hypotensive effect of octanoate. The present study investigates the octanoate action on the bioelectric and contractile activity of vascular smooth muscle tissues. Octanoate is shown to cause hyperpolarization of smooth muscle cells, reduction of spike potential frequency, and relaxation of vascular muscles. These effects are inhibited by indomethacin, which proves their prostaglandin nature. Octanoate action on stomach smooth muscle strips is inhibited by SC 19220, a specific competitive inhibitor of the contractile action of prostaglandins E2 and F2 alpha on the same tissues in vitro. Using thin-layer chromatography two PG fractions were isolated from arterial blood of octanoate treated rats and from a control group of rats. These fractions have identical chromatographic characteristics with those of PGE2 and PGF2 alpha. The level of the PG fraction with Rf value similar to that of PGE2 is significantly increased in octanoate treated animals while the other fraction tends to decrease.