Differential effects of glycosylated and non-glycosylated porcine prolactin on estradiol and progesterone secretion by rat granulosa cells in culture

RESUMO

Background. The objetive was to better understand the interactions between prolactin and ovarian function. Methods. The effects of two variants of porcine prolactin (pPRL) on estradiol (E2) and progesterone (P4) production by rat granulosa cells in culture were studied using granulosa cells obtained from large preovulatory follicles of pregnant mare serum gonadotropin (PMSG)-treated immature Sprague-Dawley rats. Cultures were performed in the absence or presence of hCG (0.1 IU/ml) and different concentrations of either glycosylated and non-glycosylated (g-pPRL and ng-pPRL, respectively) pPRL. Results. Dose-response studies showed that maximal stimulation occurred in all instances with g-pPRL at the dose of 10 ng/mL during the 72-h treatment period. In the case of E2 the maximal response was obtained in hCG-stimulated cultures, whereas the response of P4 was higher in cultures stimulated with g-pPRL in the absence of hCG. In a similar manner, the non-glycosylated form of pPRL increased, although to a lesser extent, the secretion of P4 only in those cultures incubated in the absence of hCG. In contrast to these observations, ng-pPRL was about twice as active than the glycosylated form on the stimulation of growth of Nb2 lymphoma cells. Conclusions. These data point out that glycosylation is involved in the differential effects of pPRL on ovarian steroidogenesis and support the role of carbohydrates in the structural-functional polymorphic nature of the hormone