CONICET | Buscador de Institutos y Recursos Humanos

TGFβ1 is a known inhibitor of lactotroph cell proliferation and prolactin secretion. TGFβ1 bioavailability is tightly regulated by different components of the ?TGFβ1 system? including latent binding proteins (LTBPs), local activators, and TGFβ receptors. Pituitary TGFβ1 activity is regulated by dopamine and estradiol. We previously demonstrated that estradiol inhibits most of the component of the pituitary TGF1 system. The aim of the present work was to study the ontogeny of the pituitary TGF1 system in males and females Sprague Dawley rats at different ages: 11, 23 and 45 days. Adult females were used in diestrus. ELISAs were performed to quantify total and active TGFβ1 content in pituitary homogenates. We evaluated the expression of the components of TGFβ1 system by qPCRs. Serum prolactin was assayed by RIA. We found increased expression of total TGFβ1, TβRII, ALK1, SMAD7 and the latent proteins LTBP1 and LTBP3 in 11d pups, compared to adults, without gender differences. On the other hand, active cytokine levels were found increased in 11d females compared to 11d males and to adults. It was concomitant with elevated TGFβ1 mRNA and increased cytokine biological activity, reflected in higher expression of TGFβ1 target genes, in this group. In parallel, serum prolactin levels were low during the first month of life and gradually increased toward puberty, in both male and female rats. It was concomitant with an age-related increase in the expression of estradiol receptor alpha. We postulated that the high expression and activity of the pituitary TGF1 system found in 11d pups could be related to the immaturity of the negative control exercised on the pituitary TGF1 by estradiol. As TGF1 plays essential roles in morphogenesis, and in fully developed organisms is required for tissue homeostasis, the importance of the increased expression and activity of the pituitary TGF1 system found in infantile rats, deserves more in-depth studies.