The Effect of Coumestrol on Progesterone and Prostaglandin Production in the Mare: In Vitro and In Vivo Studies

ABSTRACT Coumestrol (Cou) is a plant-derived phytoestrogen that induces various pathologies in the female reproductive tract. Although effects of phytoestrogens on reproductive function in other species are well documented, their influence on progesterone (P4) and prostaglandin (PG) secretion in the mare is unknown. The aim of this study was to determine if Cou directly affects P4 and PG concentrations (in vivo) and endometrial PG secretion (in vitro) in the mare. In experiment 1, the mares (n = 4) were fed for 14 days on a diet containing increasing proportions of alfalfa pellets (250 g–1 kg/day). An additional 4 mares were fed a standard diet (control group). Sequential blood samples were obtained for 8 h after feeding on Days 13 and 14 (1 kg/day alfalfa pellets). Feeding the mares alfalfa pellets up-regulated PGE2 and 13,14-dihydro-15-ketoprostaglandin F2alpha (PGFM) and down-regulated P4 in the blood plasma compared to those in the control group (P < 0.05). In experiment 2, epithelial and stromal cell...