1alpha,25-Dihydroxyvitamin D-3 (1alpha,25(OH)(2)D-3) increases the binding of transforming growth factor beta1(TGF beta1) via TGF beta receptors to the surface of human osteoblasts. The increase in TGF beta receptors induced by 1alpha,25(OH)(2)D-3 is dependent on increases in TGF beta secretion induced by 1alpha,25(OH)(2)D-3, since antibodies directed against TGF beta block the increase in TGF beta1 binding. The increase in TGF beta type I and 11 receptors on cell surfaces following 1alpha,25(OH)(2)D-3 treatment is associated with increases in receptor mRNA concentrations. Increases in receptor mRNA concentrations following 1alpha,25(OH)(2)D-3 treatment are not due to changes in receptor gene transcription. The role of TGF beta receptors, in mediating the growth responses to 1alpha,25(OH)(2)D-3 is demonstrated by showing that osteoblasts which express dominant negative, kinase-deficient TGF beta type 11 receptors, fail to respond to the growth-inhibitory effects of 1alpha,25(OH)(2)D-3. An increase in TGF beta receptor expression is important in mediating 1alpha,25(OH)(2)D-3-associated changes in the growth rate of osteoblasts. (C) 2002 Elsevier Science (USA).