Bovine somatotropin attenuates phorbol ester-induced prostaglandin F2α production in bovine endometrial cells

The recent observation that bovine somatotropin (bST) treatment at a timed insemination improves pregnancy rates in lactating dairy cows raises the possibility that growth hormone (GH) may modulate the endocrine and biochemical cross talk between the conceptus and maternal uterus at the time of pregnancy establishment in cattle. The objective of this study was to characterize the cellular and molecular mechanisms by which exogenous GH affects phorbol ester-induced prostaglandin F-2alpha (PGF(2alpha)) production in cultured bovine endometrial (BEND) cells. Serum-deprived BEND cells were incubated with or without recombinant bovine GH (rbGH), insulin-like growth factor (IGF)-I, recombinant bovine interferon (rbIFN)-tau or a combination of rbGH + rbIFN-tau for 3 h and then treated with phorbol 12,13-dibutyrate (PDBu) for an additional 6 h. Exogenous PDBu increased PGF(2alpha) secretion and steady-state levels of COX-2 mRNA within 3 h. Priming of BEND cells with rbGH reduced PGF(2alpha) response to PDBu, whereas cotreatment with IGF-I amplified PDBu induction of PGF(2alpha). Preincubation of cell monolayers with rbIFN-tau suppressed PGF(2alpha) and COX-2 mRNA responses to PDBu. Inhibitory effects of rbGH and rbIFN-tau on PDBu-induced PGF(2alpha) production were additive. Results provide the first direct evidence that supplemental bST may interact with conceptus-secreted IFN-tau to modulate PGF(2alpha) secretion at the critical time of maternal recognition of pregnancy.