Abstract
We investigated the effects of hepatocyte growth factor (HGF) and platelet-derived growth factor (PDGF) on the expression of α2- and β2-adrenergic responses in primary cultures of adult rat hepatocytes. HGF (1 and 5ng/ml) rapidly stimulated the expression of β2-adrenergic responses and significantly increased α2-adrenergic responses with a maximal response at 21h. The stimulatory effects of HGF were reduced dependent on the initial plating density and were completely blocked by cycloheximide (5μM). On the other hand, PDGF (10ng/ml) significantly increased the β2-adrenergic response, but only slightly increased the α2-adrenergic responses. Expression of the α2- and β2-adrenergic responses by PDGF was independent of the initial plating density. The expression of these responses was blocked by cycloheximide (5μM). Northern blot analysis of the hepatocyte mRNA showed increased expression induced by the HGF and PDGF of the both α2- and β2-adrenergic receptor mRNA, and this expression was inhibited by actinomycin D (5ng/ml). These results indicate that the expression of α2- and β2-adrenergic responses produced by these two growth factors is regulated differently by the cell density of the primary cultures. The results suggest that the expression of α2- and β2-adrenergic responses is mediated through increased synthesis of these receptor proteins.
