CONICET | Buscador de Institutos y Recursos Humanos

TGFβ1 and activins are known inhibitors of lactotroph function. We previously studied the pituitary expression of several components of these inhibitory systems during postnatal development in rats. We found that 11 days-old females present stronger pituitary TGFβ1 and activin systems compared to males and older females. Only in females pituitary expression of those systems inversely correlates with serum prolactin levels during postnatal development. Since dopamine (DA) and estradiol (E2) are the main regulators of lactotroph function, the aim of the present work was to study the estrogenic and dopaminergic regulation of pituitary TGFβ1 and activin systems at early postnatal age. To this end, 11 days-old Sprague Dawley rats were injected with E2 valerate (0.2mg/kg, sc), cabergoline (DA agonist, 2mg/Kg, ip), sulpiride (DA antagonist, 5mg/kg, ip) or vehicle (castor oil or saline). After three hours, animals were euthanized and pituitary expression of TGFβ1 and activin systems components was evaluated by RTqPCR. Statistical analysis: two-way ANOVA, followed by post hoc Tukey test. We found that E2 increased pituitary mRNA expression of most of TGFβ1 and activin systems components evaluated (TGFβ1, TβRII, βA and βB subunits, ActRIIB, ALK4 and FST) in both females and males. On the other hand, sulpiride treatment significantly decreased pituitary TGFβ1, TβRII, βA-subunit and FST expression in both genders; while cabergoline treatment had no effect on TGFβ1 and TβRII pituitary expression but increased expression of βA-subunit and FST. Taken together, the present results indicate a strong positive regulation by E2 and DA on both inhibitory systems of lactotroph function at early postnatal days, and suggest that the hormonal environment at 11 days-old could be determining the gender differences found in the pituitary expression of TGFβ1 and activin systems.