Abstract
Abstract
Incubations of rat anterior pituitary cells with transforming growth factor (TGF)-β1 for 48 hr suppressed the secretion of basal prolactin (PRL) in a dose-dependent manner (ED50, 100 pg/ml). Activin, a gonadal hormone processing cysteine distribution similar to TGFβ, also suppressed basal PRL secretion, but it was less effective (ED50, 4 ng/ml). Treatment with TGFβ1 significantly suppressed basal PRL secretion from the pituitary after 24 hr and up to 72 hr of incubation. TGFβ1 also inhibited thyrotropin-releasing hormone-mediated PRL secretion and activin inhibited thyrotropin-releasing hormone-mediated PRL secretion slightly, but significantly. In addition, we also measured the secretion of growth hormone by cultured pituitary cells treated with TGFβ1 or activin for 24 to 72 hr. TGFβ1 and activin showed an opposite effect on growth hormone secretion; TGFβ stimulated and activin inhibited basal secretion of growth hormone. These results suggest that TGFβ1 is a potent inhibitor of basal secretion of PRL by the pituitary, and both TGFβ1 and activin play a multifunctional role in basal secretion of pituitary hormones.
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