Prostaglandin I 2 is less relaxant than prostaglandin E 2 on the lamb ductus arteriosus

Abstract

Prostaglandin(PG) I 2 and its stable metabolite, 6-keto-PGF 1α, were tested on the isolated ductus arteriosus from mature fetal lambs. PGI 2 relaxed the ductus in high doses (threshold 10 −6M) and its activity disappeared on standing at room temperature for 30 minutes. 6-keto-PGF 1α was inactive at all doses. By contrast, PGE 2 produced a dose-dependent relaxation over a range between 10 −10 and 10 −6 M. These findings confirm that PGE 2 is the most potent ductal relaxant among the known derivatives of arachidonic acid. PGE 2 probably maintains ductus patency in the fetus and, together with PGE 1, remains the compound of choice in the management of newborns requiring a viable ductus for survival.