Contributions to the mechanism of action of beta-adrenergic stimulants.

Subcellar localization of ionic Ca was investigated by the Pb-acetate cytochemical method in rat myometrium on the 21st day of pregnancy, following oxytocin and Bricanyl treatment. Following Oxytocin treatment the amount of ionic Ca increased in the muscle cells of the uterus and decreased in the plasma membrane and mitochondria as compared with the control. Tocolytics given in the last four days of pregnancy caused a decrease in the cytoplasmic concentration of ionic Ca and increased the Ca++ content of Ca++ pools (plasma membrane, mitochondrium). The change in the intracellular distribution of Ca++ may be involved in the mechanism of action of tocolytics and in the development of the relaxation of smooth muscle.