Lungs as a generator of prostacyclin--hypothesis on physiological significance.

In vivo anti-platelet de-aggregatory activity of exogenous prostacyclin is enhanced after its passage through the pulmonary circulation of anaesthetized cats, probably because of a concomitant generation of endogenous prostacyclin by the lungs. Evidence is also presented that perfused lungs of guinea pigs and rats spontaneously release considerable amounts of prostacyclin. It is therefore postulated that a continuous biosynthesis of prostacyclin by pulmonary endothelium is a general physiological phenomenon, while the generation of thromboxane A2 by lungs occurs in response to pathological stimuli. Coronary and cerebral arteries are supposed to benefit from this hormonal function of the lungs.