To understand and regulate uterine contraction/relaxation, it is important to understand the mechanisms that control intracellular Ca. Proteins in the Trp family are postulated to form store operated and non-capacitative calcium channels. The overall goal of this study is to test the hypothesis that, by forming channel complexes that respond to contractant-stimulated signals related to intracellular Ca store depletion, Trp proteins contribute in a significant way to Ca entry in myometrium. Our preliminary data indicate that multiple Trp proteins are expressed in myometrial cells. Aim 1 will examine the expression of specific Trp mRNA forms and Trp proteins in human myometrial PHM1-41 cells and will include completion of Trp cDNA sequences, examination of alternative splicing patterns, and quantitation of the relative expression of these mRNAs by Q-RT-PCR. Aim 2 will examine the function of Trp proteins in relation to capacitative calcium entry in myometrium. The effects of overexpressing selected Trp proteins in human myometrial cells on intracellular Ca transients and Ca entry in depletion/readdition protocols stimulated by G- protein coupled receptor activation or intracellutar Ca pump inhibition will be measured by dual wavelength fluorescence imaging with Fura-2 as indicator. The consequences of inhibition of specific Trp protein expression by Trp antisense mRNA on calcium dynamics will be assessed. The relative importance of voltage-operated versus capacitative calcium entry in rat myometrial tissue will be assessed in a number of protocols employing simultaneous measurement of changes in force and intracellular Ca. Aim 3 will examine the regulation of Trp mRNAs and protein expression during pregnancy in the rat and human and by hormones in PHM1-41 cells in culture. The studies proposed here will provide important new insights into the potentially important role of these proteins in the myometrium. The regulation of the activity of these proteins may provide a new target for drugs regulating contractile activity and hence may prove useful in the control of premature labor and dysfunctional labor.