FORMATION AND ACTION OF PROSTAGLANDIN ENDOPEROXIDES IN ISOLATED HUMAN UMBILICAL ARTERY

The effects on the isolated human umbilical artery (HUA) of the recently isolated endoperoxide intermediates in prostaglandin (PG) biosynthesis, PGG2 and PGH2, were studied. Both endoperoxides were potent contractors of the artery strips, the threshold concentrations being 3 (1-4) ng/ml for PGG2 and 1 (1-12) ng/ml for PGH2, as compared with 200 (40-400) ng/ml for PGE2. The hemiacetal derivative of 8-(1-hydroxy-3-oxopropyl)-9,12L-dihydroxy-5,10-heptadecadienoic acid (thromboxane B2), a metabolite of PGG2, appeared in the bath medium, indicating PG and thromboxane generation in the isolated HUA. The formation of thromboxane B2 was inhibited by indomethacin (8-40 .mu.g/ml) and by eicosa-5,8,11,14-tetraynoic acid (ETA) (25 .mu.g/ml). ETA also inhibited the contractile responses to both endoperoxides. Local generation of PG might be involved in the closure of the HUA at birth.