Abstract
The objective of our study was to examine the direct effects of the medicinal plant Tribulus terrestris L. (puncturevine) on the basic functions of ovarian cells, including their proliferation, apoptosis, and response to the physiological hormonal stimulator ghrelin. In the first series of experiments, porcine ovarian granulosa cells were cultured with or without puncturevine extracts at concentrations of 0, 1, 10, or 100 mu g/ml. In the second series of experiments, these cells were cultured with ghrelin at concentrations of 0, 1, 10, or 100 ng/ml, either alone or in combination with puncturevine (10 mu g/ml). The expression levels of the proliferation marker PCNA and the apoptosis marker bax were analyzed via quantitative immunocytochemical methods. Puncturevine was found to stimulate the accumulation of both proliferation and apoptotic markers. Additionally, ghrelin alone could promote the proliferation and apoptosis of ovarian cells. The presence of puncturevine reversed ghrelin-stimulated apoptosis and instead induced apoptotic inhibition. However, puncturevine did not modify the proliferation-inducing effect of ghrelin. These observations demonstrated that (1) puncturevine directly promotes cell proliferation and apoptosis, turnover, of ovarian cells; (2) ghrelin is involved in the regulation of ovarian cell apoptosis and proliferation, consistent with existing evidence; (3) puncturevine antagonizes and even reverses the effects of the hormonal regulator, ghrelin, on ovarian cell apoptosis, but not proliferation; and (4) puncturevine affects not only the basic functions of ovarian cells but also their responses to upstream hormonal regulators.