Abstract
Differentiating mouse 3T3-L1 preadipocytes have been used as a model system to study the ability of type beta transforming growth factor (TGF-beta) to modulate cell development. We find that TGF-beta inhibits potently (ID50 approximately equal to 25 pM) the adipogenic conversion of 3T3-L1 cells. Inhibition is observed only when cells are exposed to TGF-beta before they become committed to differentiation. Even a transient (4 hr) exposure to TGF-beta immediately before the commitment point is sufficient to prevent differentiation. This point coincides with the time point immediately preceding the onset of coordinate expression of differentiation-specific proteins in 3T3-L1 cells. TGF-beta interacts with cell surface receptors in 3T3-L1 cells that have structural and binding properties similar to TGF-beta receptors in other cell types in which TGF-beta acts as a growth activator or a growth inhibitor. However, TGF-beta does not markedly alter differentiation-related mitosis in 3T3-L1 cells. The action of TGF-beta on 3T3-L1 cells does not involve changes in cAMP or prostaglandin E levels. These results suggest that TGF-beta is a unique modulator of adipogenic differentiation of fibroblasts.