Relaxin increases calcium efflux from rat myometrial cells in culture.

Relaxin and isoproterenol treatment rapidly increased 45Ca2+ efflux from mature rat myometrial cells in culture in a time- and concentration-dependent manner. This effect on Ca2+ efflux was specific for myometrial cells and was not observed in stromal cells isolated from the same uteri. This rapidly exchangeable Ca2+ may be mobilized from a loosely bound peripheral Ca2+ pool in myometrial cells. Relaxin may promote uterine relaxation in part by affecting Ca2+ dynamics in the myometrium.