Prostaglandins in the circulation of the fetal lamb.

Prostaglandin E and PGF have been measured in the plasma of chronically catheterized fetal lambs throughout the last 20-35 days (0.73 onwards) of gestation. The mean concentration of PGE was higher than that of PGF. There was a significant increase in the concentration of PGE but little change in the concentration of PGF in samples of fetal plasma taken within 24 h of parturition. In contrast, at this time in maternal utero-ovarian venous plasma, there was a large increase in PGF, but relatively little change in PGE. There was a significant decrease in the concentration of PGE and PGF in the plasma of lambs within 12 h after birth compared to the levels found in the same animals as fetuses a few hours previously. The physiological importance of these changes is discussed.