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These studies sought to test the hypothesis that prostaglandin F2α(PGF2α)-stimulated phasic myometrial contractions are characterized by the activation of the phosphatidylinositol-signaling pathway resulting in the generation of cytosolic calcium oscillations. For the experiments described in this report rat myometrial tissue was used, after the tissue was loaded with fura 2, to perform cytosolic calcium imaging studies and to perform computer-digitalized in vitro isometric contraction studies. Consistent with the above hypothesis, the cytosolic calcium-imaging studies demonstrated PGF2α-stimulated cytosolic calcium oscillations occurring simultaneously with phasic contractions. The in vitro isometric contraction studies confirmed that previously reported inhibitors of the phosphatidylinositol-signaling pathway and cytosolic calcium oscillation mechanisms resulted in significant inhibition of PGF2α-stimulated phasic myometrial contractions. In summary, these studies have provided substantial support for the hypothesis that PGF2α-stimulated phasic myometrial contractions are generated by intracellular signaling mechanisms involving activation of the phosphatidylinositol-signaling pathway and the production of cytosolic calcium oscillation-like phenomena.

We confirmed that thrombin and thrombin produced by actively clotting blood had a robust uterotonic effect in the rat and that prostaglandin production did not play a significant role in thrombin-stimulated contractions.