Effect of prostaglandin E₂ (PGE₂) on the release of gonadotropin-releasing hormone (GnRH) from infundibular explants of cattle

Abstract

GnRH neuronal terminals located in the infundibulum of rodents have been shown to release GnRH when stimulated with PGE₂ in vivo and in vitro. The effect of PGE₂ on the release of GnRH has not been determined in cattle. Thus, the objective of this study was to test the hypothesis that PGE₂ can induce a release of GnRH from bovine infundibular explant halves incubated in vitro similar to release observed in rats. Infundibular explant halves from steers were incubated for nine thirty-minute periods (a total of 270 minutes) in Krebs-Ringer bicarbonate medium (KRB) with or without PGE₂ in 95% ethanol (2.4% of media volume) or 60 mM K⁺ in KRB at 37⁰C and saturated with 95% O₂-5% CO₂. PGE₂ was administered at concentrations of 0 []M (control for time period six), 100 []M, and 1000 []M (time period six) and compared to control (time period five). Neither of the PGE₂ treatments (0 []M, 100 []M, or 1000 []M) affected the release of GnRH. Consequently, a dose dependent effect of PGE₂ on the GnRH release was not observed. Depolarization (time period eight) (60 mM K⁺) induced an increase (p < .001) in GnRH release, when compared to control (time period seven). These depolarization responses are consistent with responses previously observed from rodent and bovine explants, thus providing evidence that the explants in this experiment were capable of releasing GnRH. These results suggest that PGE₂ is unable to stimulate GnRH release from bovine infundibular explant halves incubated in vitro. Thus, they do not support a role of PGE₂ in release of GnRH from the infundibulum of cattle.