Selective Passage of Prostaglandins across the Lung

TLDR: The removal of prostaglandins by the lung restricts their activities to the organs from which they are released and between their organ of origin and the site in the pulmonary circulation where they are inactivated.

Abstract: STIMULATION of the splenic nerves releases prostaglandins from the spleen to give concentrations of as much as 0.2 µg/ml. in splenic venous blood1. The release of prostaglandins might influence organs remote from the site of release, for prostaglandins can exert potent actions on smooth muscle2. The lung has recently been shown to determine the fate of many vasoactive substances; some are activated—conversion of angiotensin I to angiotensin II (ref. 3)—and some inactivated. The degree of inactivation seems to be specific for a given substance, ranging from almost complete (bradykinin4, 5-hydroxytryptamine5, prostaglandins E1 E2 and F2α (ref. 1)), to minor (noradrenaline6), to allowance of their free passage (adrenaline6 and angiotensin II (ref. 7)). The removal of prostaglandins by the lung restricts their activities to the organs from which they are released and between their organ of origin and the site in the pulmonary circulation where they are inactivated1. A prostaglandin which passed through the lungs after its release from an organ could be considered a circulating hormone, as long as it is not rapidly degraded in the blood. Ferreira and Vane1 reported that prostaglandins E1 E2 and F2α were stable in blood, though rapidly inactivated by the lung. Removal of prostaglandins A1 and A2 by the lung was not determined because the assay organs are insensitive to them. Vascular smooth muscle, however, unlike other smooth muscle, is reactive to low concentrations of prostaglandins A1 and A2 (refs. 8–10) and the renal vasculature is probably most sensitive to prostaglandins A1 and A2 (refs. 10 and 11). Because the renal vasculature is also sensitive to prostaglandins E1 and E2 (ref. 12), it has been used as an index of the fate of prostaglandins infused into the venous and arterial circulations.