Alpha-1 adrenergic receptor number and receptor density in isolated hepatocytes from foetal, juvenile and adult rats

Abstract

Alpha-1 adrenergic receptor number was defined by [ 3H]-prazosin binding in crude membrane preparations of hepatocytes and in intact hepatocytes isolated from foetal (day 22 of gestation), juvenile (12 days old), adult female and adult male (90–150 days old) rats and compared with the alpha-1 adrenergic response (measured by epinephrine stimulated glucose liberation in presence of the beta-antagonist propranolol). The alpha-1 receptor number (expressed as fmol bound [ 3H]-prazosin/mg membrane protein or as receptor number/cell) increases in an age-dependent fashion reaching the highest values in hepatocytes of adult female and male rats. Statistically significant differences could be found between foetal, juvenile and adult rat hepatocytes. No differences in [ 3H]-prazosin binding were observed between hepatocytes of adult female and adult male rats. The receptor density (expressed as receptor number/μm 2 cell surface), however was found to be equal in juvenile and adult rats. There are no differences of alpha-1 adrenergic response in juvenile, adult female and adult male rat hepatocytes, whereas the values in foetal hepatocytes were significantly lower. So the biological response is closely correlated with the receptor density and not with the receptor number per cell.