Through the use of inhibitory analysis by using the fluorescent probe chlortetracycline examined the effects of estradiol on the mobilization of Ca2+ from intracellular stores of porcine oocytes stimulated by growth hormone and theophylline. It is shown that somatotropin or theophylline stimulates the mobilization of Ca2+ from intracellular stores of oocytes in control group, while their combined action does not lead to an additional exit of Ca2+ from intracellular stores. Inhibitor of protein kinase C had no effect on the release of Ca2+--from oocyte stimulated by growth hormone or theophylline. In estradiol-treated oocytes, only the combined effects of growth hormone and theophylline stimulates the release of Ca2+ from intracellular stores, and that the release of Ca2+ is reduced by the use of an inhibitor of protein kinase C. In the presence of estradiol, an inhibitor of microtubule polymerization blocked the release of Ca2+ stimulated by the combined action of growth hormone and theophylline. Incubation of oocytes in the medium with the subsequent addition of ADP and GDP have an inhibitory effect on the release of Ca2+ from intracellular stores, stimulated joint action of growth hormone and theophylline. The findings suggest the involvement of estradiol in the mechanisms of calcium signaling in porcine oocytes.