Role of endogenous and exogenous prostaglandins on the contractile functioning of isolated sow (Sus scrofa) oviducts

The output prostaglandins (PHs) E₁, E₂ and F₂ α, from ampullary and isthmic portions of sow oviducts isolated during proestrus, estrus and metestrus, was explored. Moreover, $\text{in vitro}$ cumulative dose-response curves for the contractile effect of these three PGs, on identical oviductal segments, were constructed. Isthmic preparations form proestrous and metestrous animals released more PGE₁ and PGF₂ α than PGE₂ “like material”. During estrus, the outputs of PGE₁, PGE₂ and PGF₂ α were similar, whereas, oviducts from proestrous and metestrous sows released less PGE₁ and PGF₂ α than during estrus. Although the output of PGE₂ “like material” from isthmic and ampullary segments did not differ significantly during the three stages of the sex cycle, ampullary metestrous preparations released more PGE₁ and PGF₂ α, than estrous or proestrous ones. The addition of PGE₁, PGE₂ α, consistently stimulatedthe amplitude of contractions of isthmic oviductal segments isolated from proestrous and metestrous sows. Within the concentration-range explored, dose-response curves for PGE₂ and PGE₁ were to the left of those for PGF₂ α in the isthmus obtained before ovulation (proestrus) but not in segments isolated at later times (2–3 days) of the cycle (metestrus). The stimulatory dose-response curves for PGE₁, or PGE₂, in isthmic segments of metestrous preparations incubated with phentolamine (10^?6M) were shifted to the right of controls not exposed to the adrenoreceptor blocker, whereas, the curve for PGF₂ α without phentolamine, was identical to that obtained in its presence. PGE₁ and PGE₂ did not evoke significant contractile effects on oviductal ampullary protions from proestrous sows, wherea, PGF₂ α was clearly stimulatory at concentrations of 10^?9M and higher. In ampullary segments isolated after ovulation (metestrus) the threshold for contractile enhancement following PGF₂ α was greater than during proestrus, whereas, PGE₁ elicited a significant inhibition of contractions. The spontaneous contractile pattern exhibited by isthmic and ampullary oviductal regions, prior to and after ovulation, is discussed in terms of tissue PG generation and output and is compared with results regarding tubal motility following the exposure to exogenous PGs.