Isoprenaline stimulates gene transcription of the inhibitory G protein α-subunit Giα-2 in rat heart

Abstract

In vitro transcription reactions were performed with isolated ventricular nuclei of adult rats to investigate whether increased mRNA levels of the inhibitory G protein α-subunit Giα-2 after prolonged in vivo stimulation with the β-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 Giα-2 and the stimulatory G protein α-subunit Gsα were specific and due to hybridization of nascent mRNA transcripts. In the isoprenaline group the transcriptional activity of Giα-2 gene increased to 140% of the control value, whereas gene specific hybridization for Gsα remained unchanged. These results show that increased Giα-2 mRNA levels after stimulation with isoprenaline are at least partially caused by enhanced transcription of Giα-2 mRNA.