[Effects of steroid hormones on change in [Ca2+]i and on PI response following oxytocin stimulation in cultured human myometrial cells].

In oxytocin (OT)-induced myometrial contraction, it is considered that Ca2+ release associated with activation of PI response is the main cascade. Steroid hormones such as dehydroepiandrosterone-sulfate (DHAS), progesterone (P), and cortisol (F), which show diverse changes during pregnancy, are considered to be involved in myometrial contraction at the onset of delivery. In this study, we examined changes in the intracellular Ca2+ concentration ([Ca2+]i) and PI response under OT stimulation. (1) After cultured human myometrial cells were incubated for 48 hours in a medium containing 10(-6) M of DHAS, P, or F, [Ca2+]i was measured with an OLYMPUS OSP3 by using the fluorescent Ca2+ indicator Fura2-AM. When the maximum change in [Ca2+]i under stimulation with 10(-8) M OT was regarded as 100% (control), it was increased significantly to 121.1 +/- 9.8% in the cells treated with F, but was reduced to 89.4 +/- 4% in those treated with P. It was increased to 107.5 +/- 6.9% in the cells treated with DHAS, but the difference was not significant. (2) After loading with 5 microCi 3H myo-inositol and various steroid hormones for 24 hours in the cells, the intracellular IP1-3 production under stimulation with 10(-8) M OT was examined. IP1-3 production and IP total production (IPn) were significantly increased in the cells treated with F as compared with the control, but IPn was reduced by about 40% in the cells treated with 10(-6) M P. And in the cells treated with DHAS, IPn was slightly increased.(ABSTRACT TRUNCATED AT 250 WORDS)