DIFFERENTIAL-EFFECTS OF GLYCOSYLATED AND NONGLYCOSYLATED PORCINE PROLACTIN ON ESTRADIOL AND PROGESTERONE SECRETION BY RAT GRANULOSA-CELLS IN CULTURE

Background: The objective was to better understand the interactions be tween prolactin and ovarian function. Methods: The effects of two vari ants of porcine prolactin (pPRL) on estradiol (E-2) and progesterone ( P-4) production by rat granulosa cells in culture were studied using g ranulosa cells obtained from large preovulatory follicles of pregnant mare serum gonadotropin (PMSG)-treated immature Sprague-Dawley rats, C ultures were performed in the absence or presence of hCG (0.1 IU/ml) a nd different concentrations of either glycosylated and nonglycosylated (g-pPRL and ng-pPRL, respectively) pPRL. Results : Dose-response stud ies showed that maximal stimulation occurred in all instances with g-p PRL at the dose of 10 ng/mL during the 72-h treatment period, In the c ase of E-2, the maximal response was obtained in hCG-stimulated cultur es, whereas the response of P-4 was higher in cultures stimulated with g-pPRL in the absence of hCG, In a similar manner, the non-glycosylat ed form of pPRL increased, although to a lesser extent, the secretion of P-4 only in those cultures incubated in the absence of hCG. In cont rast 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 t he differential effects of pPRL on ovarian steroidogenesis and support the role of carbohydrates in the structural-functional polymorphic na ture of the hormone.