Effects of Bovine Somatotropin on Uterine Genes Related to the Prostaglandin Cascade in Lactating Dairy Cows*

Multiparous Holstein cows, averaging 80 d in milk, were used to examine the effect of exogenous bovine somatotropin (bST) on uterine expression of estrogen receptor α (ERα), prostaglandin endoperoxide synthase-2 (PGHS-2), and peroxisome proliferator-activated receptor δ (PPARδ). About 12 h before expected ovulation in a synchronization protocol, cows were assigned to receive bST (500 mg, n = 11) or serve as untreated controls (n = 10). Cows that ovulated (n = 9 bST, 8 control) were divided within treatment to be killed on d 3 or 7 postovulation. Samples of intercaruncular endometrial tissue from uterine horns ipsilateral to the corpus luteum were collected and stored at −80°C for subsequent mRNA analyses. Endometrial concentrations of ERα and PGHS-2 mRNA transcripts were greater on d 7 than on d 3 of the estrous cycle, but did not differ between treatments. Compared with untreated cows, short-term bST treatment decreased PGHS-2 protein expression at d 7 of the estrous cycle. Concentration of PPARδ mRNA transcript in the uterus decreased between d 3 and 7 of the estrous cycle and was negatively correlated with ERα and PGHS-2 mRNA concentrations. Short-term administration of bST to lactating dairy cows had minimal effects on uterine genes encoding ERα, PGHS-2, and PPARδ at d 3 and 7 of the estrous cycle but there may be an inverse relationship between PPARδ and uterine expression of ERα and PGHS-2 genes.