REGULATION OF ALPHA(1B)-ADRENERGIC RECEPTOR GENE-EXPRESSION IN RAT-LIVER CELL-LINES

alpha(1b)-Adrenergic receptor gene expression was investigated in two rat hepatic cell lines, Clone 9 and McA-RH7777 cells. By Northern blot analysis, Clone 9 cells expressed a 2.7 kb alpha(1b)-adrenergic recep tor gene transcript whereas two transcripts, 3.3 kb and 2.7 kb, were o bserved in total cellular RNA isolated from rat liver. A binding site for the alpha(1)-adrenergic antagonist [H-3]prazosin was observed in C lone 9 cell membrane preparations (B-max = 47 +/- 7 fmol/mg protein an d K-d = 0.11 +/- 0.02 nM, n = 5). In contrast, alpha(1b)-adrenergic re ceptor gene transcripts could not be detected in total cellular RNA pr epared from McA-RH7777 cells by either Northern blot analysis or ribon uclease protection assays. However, results from nuclear run-off assay s indicated that the alpha(1b)-adrenergic receptor gene was transcribe d in McA-RH7777 cells and alpha(1b)-adrenergic receptor gene transcrip ts were observed in McA-RH7777 cell nuclear RNA. These results suggest that alpha(1b)-adrenergic receptor gene expression in liver may be re gulated in part post-transcriptionally and that this level of regulati on may be altered or disrupted in the Clone 9 and McA-RH7777 cell line s.