Mass-spectrometric evidence for spontaneous and angiotensin-induced generation of prostacyclin by perfused cat lungs.

Isolated perfused cat lungs secreted spontaneously a PGI2-like substance that relaxed a strip of bovine coronary artery. The presence of PGI2 was confirmed by the identification of 6-oxo-PGF1 alpha by GC-MS. Both bioassay and mass fragmentography showed that PGI2 was released at a rate of 4 - 12 ng/ml. Generation of PGI2 by the perfused cat lungs was stimulated by angiotensin II (3 - 10 ng/ml). The above results along with our in vivo experiments point to the lung as an important source of endogenous PGI2 in the body.