Uterine vein prostaglandin levels in late pregnant dogs

Abstract

We studied the uterine venous plasma concentrations of prostaglandins E 2, F 2α, 15 keto 13,14 dihydro E 2 and 15 keto 13,14 dihydro F 2α in late pregnant dogs in order to evaluate the rates of production and metabolism of prostaglandin E 2 and F 2α 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 E 2 and 15 keto 13,14 dihydro E 2 were 1.35±.27 ng/ml and 1.89±.37 ng/ml, respectively; however, we could not find any prostaglandin F 2α and very little of its plasma metabolite in uterine venous plasma. Since uterine microsomes can generate prostaglandin F 2α and E 2 from endoperoxides, prostaglandin F 2α production in vivo must be regulated through an enzymatic step after endoperoxide formation. Prostaglandin E 2 is produced by pregnant canine uterus in quantities high enough to have a biological effect in late pregnancy; however, prostaglandin F 2α does not appear to play a role at this stage of pregnancy.