Effects of d-cloprostenol on different layers and regions of the bovine uterus during the follicular and luteal phases.

Introduction: D-cloprostenol is a synthetic PGF2a, commonly used in bovine reproduction, that increases myometral contractility. However, little is known regarding its contractile behaviour and how it depends on the reproductive state and uterine topography (regions and muscular layers). Hypothesis and objectives: These aspects would affect the action of d-cloprostenol on the uterus. Therefore, we hypothesize a possible use of this drug at the time of artificial insemination, to improve conception rates and, in the post-partum, in order to accelerate uterine involution in dairy cattle. The purpose of the present study was to investigates the modulatory effect of d-cloprostenol on contractility of the bovine uterine region (horn and corpus) and their muscle layers (circular and longitudinal), in follicular and luteal phases. To our knowledge, motility effects of d-cloprostenol on different regions from healthy bovine uterus have not been described up to now. Materials and methods: Uterine specimens were collected from uterine body and horn of cattle in the follicular (n ¼ 28) and luteal phase (n ¼ 32) of the estrous cycle at slaughter. Two strips were prepared from each regions corresponding to the circular and the longitudinal muscular layers, respectively. Samples were cultured in an organ bath, exposed to synthetic prostaglandin (1 mM d-cloprostenol) and their contractile activity was monitored for 10 min. The functionality of the strip throughout the experiment was tested by a dose of carbachol (105 M). Results: The mean basal amplitude of contractions was higher in the follicular compared to the luteal phase in uterine horn samples, but not in muscles collected from the uterine body. The amplitude of contractions increased after d-cloprostenol administration in all tissues with a greater increase in samples from cattle in the follicular phase. The frequency of contractions increased after d-cloprostenol administration in longitudinal but not in circular fibrees. Conclusion: The contractile responses to d-cloprostenol in both horn and corpus were strongest in the circular muscles but weak in the longitudinal muscles.