Tissue-specific protein kinase C isoform expression in rat uterine tissue

Activation of the phosphatidylinositol signaling pathway plays a key role during the generation of agonist-stimulated phasic myometrial contractions. Protein kinase C (PKC), a component of this signaling pathway, has been previously shown to produce feedback inhibition of agonist-stimulated myometrial contractions. The studies described in this report were performed to survey the tissue-specific expression of several PKC isoforms in the rat uterus.

Uterine tissue was obtained from timed pregnant and normally cycling adult female Sprague-Dawley rats. Immunohistochemical studies were performed using the Vectastain ABC immunostaining technique and PKC isoform-specific polyclonal antibodies. Western blot studies were performed using myometrial tissue separated into cytosol and membrane fractions by differential centrifugation.

These studies confirmed significant expression of the PKC-alpha, -beta 2, -delta, -eta, and -zeta isoforms in myometrium from pregnant and estrus rats, whereas only trace or no expression of the PKC-beta 1, -gamma, -epsilon, and -theta isoforms was observed. Expression of the PKC-alpha, -beta 2, and -eta isoforms decreased modestly during the latter days of gestation; in contrast, PKC-delta and -zeta remained stable during this period. The immunohistochemical studies confirmed expression of the PKC-alpha, -beta 2, -delta, -eta, and -zeta isoforms in both circular and longitudinal smooth-muscle layers of the near-term pregnant rat uterus.

In summary, these studies have confirmed significant levels of expression of several isoforms of PKC in estrus and near-term pregnant rat uterine tissue, which was most prominent in the smooth-muscle cells of the myometrium.