ISOPRENALINE STIMULATES GENE-TRANSCRIPTION OF THE INHIBITORY G-PROTEIN ALPHA-SUBUNIT G(I-ALPHA-2) IN RAT-HEART

In vitro transcription reactions were performed with isolated ventricular nuclei of adult rats to investigate whether increased mRNA levels of the inhibitory G protein alpha-subunit G(ialpha-2) after prolonged in vivo stimulation with the beta-adrenoceptor agonist isoprenaline are caused by increased transcription. Rats were treated by a 4-day subcutaneous infusion of isoprenaline (2.4 mg/kg per day) or 0.9% NaCl as control. To avoid the influence of developmental expression patterns, adult rats were chosen for all experiments. Signals for G(ialpha-2) and the stimulatory G protein alpha-subunit G(salpha) were specific and due to hybridization of nascent mRNA transcripts. In the isoprenaline group the transcriptional activity of G(ialpha-2) gene increased to 140% of the control value, whereas gene specific hybridization for G(salpha) remained unchanged. These results show that increased G(ialpha-2) mRNA levels after stimulation with isoprenaline are at least partially caused by enhanced transcription of G(ialpha-2) mRNA.