GQ-PROTEIN ALPHA-SUBUNIT EXPRESSION AND DISTRIBUTION IN PREGNANT RAT MYOMETRIAL TISSUES

OBJECTIVE: Multiple G-protein isoforms play an integral role in signal transduction; the Gq subtype of G-protein alpha subunits is involved in the activation of the phosphatidylinositol signaling pathway. The s tudies described herein evaluate the expression of Gq, along with Gs a nd Gi, in pregnant and nonpregnant rat myometrial tissues. METHODS: My ometrium and other tissues were obtained from nonpregnant and timed-pr egnant Sprague-Dawley rats. Western blot studies were performed using polyclonal C-protein isoform-specific antibodies. Immunohistochemical studies were performed using the same antibodies with specimens of myo metrium, intestine, and skeletal muscle. RESULTS: The Western blot stu dies confirmed differential expression of all of these G-protein alpha subunit subtypes in rat myometrial tissues. In pregnant rat myometriu m, the expression of Gq and Gs was sustained through day 22, whereas, Gi expression decreased on day 20 and remained low through the remaind er of gestation. The immunohistochemical studies revealed significant staining for Gq and Gs in the myometrial layers of the pregnant and no npregnant rat uterus; in contrast, immunostaining for Gi was minimal i n nonpregnant myometrium, and even lower in myometrium from pregnant u teri. CONCLUSIONS: These studies have confirmed expression of the Gq, Gi, and Gs alpha subunits in rat myometrial tissue. Immunohistochemist ry confirmed that Gq was expressed at high levels in the myometrial la yer of the pregnant and nonpregnant uterus. These observations support the hypothesis that Gq expression is critically important for the tra nsduction of hormone signals, such as those responsible for the genera tion of phasic myometrial contractions. Copyright (C) 1997 by the Soci ety for Gynecologic Investigation.