FETAL AND MATERNAL ENDOCRINE CHANGES APPROACHING PARTURITION IN THE GOAT - LACK OF EVIDENCE FOR PROSTAGLANDINS E-2 AND F2-ALPHA AS SIGNALS FOR LUTEOLYSIS

We investigated the temporal relationship of fetal cortisol secretion to circulating concentrations of fetal ACTH(1-39) and its high-molecul ar weight precursors in goats. We also measured the concentrations of progesterone, estradiol-17 beta, estrone sulfate, prostaglandin (PG) E , PGF(2 alpha), and PGF(2 alpha) metabolite (PGFM) in maternal arteria l plasma over the last month of gestation. Prostaglandin concentration s were also measured in utero-ovarian venous plasma. There was a posit ive association between ACTH(1-39) in fetal plasma and the prepartum s urge in fetal cortisol that commenced 8 days before labor. The fetal c ortisol surge was followed by a simultaneous decrease in maternal prog esterone and an increase in plasma estrogens commencing 3-4 days befor e labor. No change in basal prostaglandin concentration occurred befor e this time. There was a positive veno-arterial difference of PGE and PGF(2 alpha) across the uterine vascular bed, confirming the uteroplac ental unit as a major source of these eicosanoids in the plasma of the pregnant doe. We conclude that the fetal signal for parturition prece des luteolysis by some 5 days and find no evidence of changes in the b asal concentrations of PGE and PGF(2 alpha) in maternal plasma at the time of luteolysis.