Expressão e localização de A/Bativina, seus receptores ActRIB e ActRIIA, de -inibinae de folistatina na glândula mamária bovina gestacional

Abstract

Gestational Expression of â Activin, ActRIB and ActRIIA Receptors, -Inhibin and Follistatin in Bovine Mammary Gland.Activins belong to the transforming growth factor superfamily and bind selectively to ActRIB and ActRIIA receptors. Their effects are antagonized by inhibins (INH) and follistatins (FS). Since activins have been related to mammary ductal elongation and lobular-alveolar differentiation in mice, we evaluated gene and protein expression of Activin-A/B subunits, ActRIB and ActRIIA receptors, FS and -INH in the mammary gland of nulliparous and pregnant heifers. Mammary glands were obtained from beef heifers slaughtered in nulliparous (NP; n=9), pregnant in the 1st (60-120 days - mammogenesis; n=9) and in the 2nd stages of gestation (150-210 days lactogenesis; n=9). Mammary tissue was analyzed by immunohistochemistry and Real Time PCR. We found a higher intensity of ductal and lobular immunostaining for A, ActRIB and ActRIIA in the mammogenesis group when compared to NP and lactogenesis groups, however the stromal cells displayed less immunostaining for A and ActRIB during lactogenesis (p<0.05, Kruskal-Wallis ANOVA and Dunns test). Activin B subunit, FS and -INH proteins were localized in ductal, lobular and stromal cells with similar intensity during all the stages. The mRNA transcripts of Activin-A/B subunits, FS and ActRIIA were expressed equally in the mammary tissue of non-pregnant and pregnant heifers. However -INH mRNA expression was up regulated during gestation and ActRIB mRNA was up regulated only during lactogenesis. In conclusion, this study firstly shows that A/B activin, ActRIB, ActRIIA, -INH and FS are expressed in stromal, ductal and lobular structures in the bovine mammary gland during non-gestational and gestational mammary gland development and differentiation.