Effects of prostaglandin F2 alpha and prostacyclin on pulmonary microcirculation in the cat

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Abstract
In pulmonary microcirculation, using a new X-ray television system, we measured the effects of prostaglandin F2.alpha. (PGF2.alpha.) and prostacyclin on the internal diameter (ID), flow velocity, volume flow, and transit times of a contrast medium in small arteries (Ta) and veins (Tv) in anesthesized cats. The ID of the arteries and veins ranged from 100 to 500 .mu.m. PGF2.alpha., 0.3, 1, and 3 .mu.g/kg, predominantly decreased ID on the arterial side in a dose-dependent manner but increased flow velocity 27-62%. Consequently, volume flow was kept relatively constant. With PGF2.alpha., Ta and Tv were decreased 18-41% and 4-15%, respectively. Prostacyclin, 2 and 4 .mu.g/kg, uniformly dilated the ID of small arteries 9-16% but did not change small veins. With prostacyclin, flow velocity was unchanged or decreased, whereas volume flow was increased significantly, 27-32%. No significant changes of Ta and Tv were observed in response to prostacyclin. When both prostaglandins, PGF2.alpha. and prostacyclin, were administered, they canceled each other with respect to the ID of small pulmonary arteries. Prostacyclin also prevented the PGF2.alpha.-induced vasoconstriction of the pulmonary venous microcirculation.