UTERINE VEIN PROSTAGLANDIN LEVELS IN LATE PREGNANT DOGS

We studied the uterine venous plasma concentrations of prostaglandins E2, F2α, 15 keto 13,14 dihydro E2 and 15 keto 13,14 dihydro F2α in late pregnant dogs in order to evaluate the rates of production and metabolism of prostaglandin E2 and F2α in pregnancy in vivo. We used a very specific and sensitive gas chromatography-mass spectrometry assay to measure these prostaglandins. The uterine venous concentrations of prostaglandin E2 and 15 keto 13,14 dihydro E2 were 1.35±.27 ng/ml and 1.89±.37 ng/ml, respectively; however, we could not find any prostaglandin F2α and very little of its plasma metabolite in uterine venous plasma. Since uterine microsomes can generate prostaglandin F2α and E2 from endoperoxides, prostaglandin F2α production in vivo must be regulated through an enzymatic step after endoperoxide formation. Prostaglandin E2 is produced by pregnant canine uterus in quantities high enough to have a biological effect in late pregnancy; however, prostaglandin F2α does not appear to play a role at this stage of pregnancy. © 1979.