Proliferation of Adult Rat Hepatocytes in Primary Cultures Induced by Platelet-Derived Growth Factor Is Potentiated by Phenylephrine

Abstract

We investigated whether or not proliferation of adult rat hepatocytes induced by platelet-derived growth factor (PDGF) is affected by alpha1-adrenoceptor agonists such as phenylephrine during the early and late phases of primary culture. Adult rat hepatocytes underwent significant DNA synthesis after culture with 10 ng/ml of PDGF for 2 hr at a low cell density (3.3 x 10(4) cells/cm2). Under these culture conditions, the number of nuclei increased significantly during the 3.5-hr culture period. Hepatocyte DNA synthesis and proliferation induced by 10 ng/ml of PDGF decreased slightly as a result of increasing the initial plating density. An alpha1-adrenoceptor agonist, phenylephrine (10(-6) and 10(-5) M), alone did not affect hepatocyte DNA synthesis and proliferation, but markedly potentiated PDGF-induced hepatocyte DNA synthesis and proliferation. The phenylephrine effect was mimicked by phorbol myristate acetate (10(-7) M), but not by ionomycin (10(-5) M). The mitogenic effects of PDGF were almost completely blocked by treating hepatocytes with genistein (5 x 10(-6) M), U-73122 (3 x 10(-6) M), sphingosine (10(-5) M), wortmannin (10(-7) M) and rapamycin (10 ng/ml). These results demonstrate that PDGF can induce the proliferation of adult rat hepatocytes rapidly in primary culture, regardless of the initial plating density. The present results also suggest that following stimulation with PDGF, activation of tyrosine kinase, phospholipase C, phosphatidylinositol 3-kinase, protein kinase C (PKC) and p70 ribosomal protein S6 kinase is essential for the proliferation of adult rat hepatocytes. The co-mitogenic effects of phenylephrine may involve PKC activation.

Activation of Mitogen-Activated Protein Kinase by Hepatocyte Growth Factor Is Stimulated by Both α1- and β2-Adrenergic Agonists in Primary Cultures of Adult Rat Hepatocytes

“…In addition, the hepatocyte DNA synthesis and proliferation produced by HGF was inhibited depending on the initial plating density. Furthermore, we found that hepatocyte DNA synthesis and proliferation were potentiated by both α 1 -and β 2 -adrenergic agonists (10).…”

“…Using specific inhibitors of signal transducers, we pharmacologically demonstrated that receptor tyrosine kinase, phosphoinositide 3-kinase, phospholipase C, and p70 ribosomal protein S6 kinase (p70S6K) activities are essential for HGF-induced DNA synthesis and proliferation in primary cultures of adult rat hepatocytes (10).…”

“…There are several types of catecholamine receptors, β 1 -and β 2 -receptors, that stimulate adenylate cyclase, while α 2 -receptors inhibit its activity (17). α 1 -Receptors are related to phospholipase C activation and subsequent increases in inositolphosphate turnover and diacylglycerol production (10,18). Although, some investigators have reported that the α 1 -and β-adrenergic responses are related to adrenergic regulation of carbohydrate metabolism in liver from normal adult rats and cultured hepatocytes (17,19,20).…”

IP Receptor Agonist–Induced DNA Synthesis and Proliferation in Primary Cultures of Adult Rat Hepatocytes: the Involvement of Endogenous Transforming Growth Factor-α

“…The number of nuclei, rather than the number of cells, was counted using a modified version of a previously described procedure (20,21). Briefly, primary cultured hepatocytes were washed twice with 2 ml of Dulbecco's phosphate-buffered saline (PBS, pH 7.4).…”

cAMP-dependent protein kinase and proliferation differ in normal and polycystic kidney epithelia

“…Effects are either mediated by cAMP-dependent protein kinase (protein kinase A, PKA; Refs. 4,12,15,26,44) or are independent of PKA and involve small guanine nucleotide binding (G) proteins (46,56,67). Both positive and negative modulation has been reported, which appeared to depend on cell type, culture conditions, or the presence of other stimuli.…”