Pharmacological characterization of beta(2)-adrenoceptor in PGT-beta mouse pineal gland tumour cells

1 The adrenoceptor in a mouse pineal gland tumour cell line (PGT-beta) was identified and characterized using pharmacological and physiological approaches. 2 Adrenaline and noradrenaline, adrenoceptor agonists, stimulated cyclic AMP generation in a concentration-dependent manner, but had no effect on inositol 1,4,5-trisphosphate production. Adrenaline was a more potent activator of cyclic AMP generation than noradrenaline, with half maximal-effective concentrations (EC50) seen at 175 +/- 22 nM and 18 +/- 2 mu M for adrenaline and noradrenaline, respectively. 3 The addition of forskolin synergistically stimulated the adrenaline-mediated cyclic AMP generation in a concentration-dependent manner. 4 The pA(2) value for the specific beta(2)-adrenoceptor antagonist ICI-118,551 (8.7 +/- 0.4) as an antagonist of the adrenaline-stimulated cyclic AMP generation were similar to 3 units higher than the value for the beta(1)-adrenoceptor antagonist atenolol (5.6 +/- 0.3). 5 Treatment of the cells with adrenaline and forskolin evoked a similar to 3 fold increase in the activity of serotonin N-acetyltransferase with the peak occurring 6 h after stimulation. 6 These results suggest the presence of beta(2)-adrenoceptors in mouse pineal cells and a functional relationship between the adenylyl cyclase system and the regulation of N-acetyltransferase expression.X1110sciescopu