Protein expression of phospholipase C in pregnant and nonpregnant rat uterine tissue

Objective: The phosphatidylinositol signaling pathway appears to play a significant role in the intracellular events leading to agonist-stimulated phasic myometrial contractions. The studies described in this report were performed to characterize phospholipase C isoform expression at the protein level and to confirm histologic localization of these proteins within the myometrial smooth muscle layers of the uterus. Methods: For these studies, uterine tissue was obtained from timed- pregnant and spontaneously cycling adult female Sprague-Dawley rats. After isolation of myometrial cell membranes and cytosolic proteins, Western blots were performed by using phospholipase C isoform-specific antibodies. Tissue cross-sections of near-term pregnant rat uterus were used with the phospholipase C isoform-specific antibodies for immunohistochemical studies. Results: The Western blot studies confirmed expression of the phospholipase C-β3, -γ1, -γ2, and -δ1 proteins in both the membrane and cytosolic fractions of rat myometrium; in contrast, only trace amounts of the phospholipase C-β1 protein was observed in this tissue. The immunohistochemical studies demonstrated localization of the phospholipase C-β3, -γ1, -γ2, -δ1 and to a lesser degree phospholipase C-β1 isoforms within the longitudinal and circular smooth muscle layers of the near-term pregnant rat uterus. Conclusion: These studies have confirmed the simultaneous expression of several phospholipase C proteins within the smooth muscle cells of the pregnant and nonpregnant rat uterus, thereby providing support for the possible redundant role of these signal transduction enzymes during the generation of cytosolic calcium oscillations and phasic myometrial contractions. (Am J Obstet Gynecol 2001;185:1191-7.)