Influence of progesterone levels on prostaglandin concentrations in isolated uterine tissue and incubation medium from pseudopregnant rats

Abstract

We measured the synthesis and secretion of uterine prostaglandins E and F 2α (PGE and PGF 2α) by the uterus in vitro from pseudopregnant (psp) rats on days 5 and 10 of psp, when level of serum progesterone was high and low, respectively. We found a direct correlation between concentration of progesterone in serum and uterine content of PGE and an inverse correlation with uterine PGF 2α. On day 5, when progesterone was high in serum, PGE increased in tissue more than in the incubation medium, suggesting a poor liberation of this PG or utilization of PGE by the tissue. On this day, no difference was seen between content of uterine PGF 2α and PGF 2α in the incubation medium. Nevertheless, on day 10, when progesterone was lower, concentrations of both PGE and PGF 2α were greater ( P < 0.001) in the medium than in the uterine tissue. However, PGF 2α in the medium was higher than PGE ( P < 0.05). The results clearly demonstrate that the synthesis and release of PGE and PGF 2α were modified by the concentration of progesterone in the serum.