Pharmacological characterization of β2-adrenoceptor in PGT-β mouse pineal gland tumour cells

The adrenoceptor in a mouse pineal gland tumour cell line (PGT-β) was identified and characterized using pharmacological and physiological approaches. 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 μM for adrenaline and noradrenaline, respectively. The addition of forskolin synergistically stimulated the adrenaline-mediated cyclic AMP generation in a concentration-dependent manner. The pA2 value for the specific β2-adrenoceptor antagonist ICI-118,551 (8.7±0.4) as an antagonist of the adrenaline-stimulated cyclic AMP generation were ∼3 units higher than the value for the βI-adrenoceptor antagonist atenolol (5.6±0.3). Treatment of the cells with adrenaline and forskolin evoked a ∼3 fold increase in the activity of serotonin N-acetyltransferase with the peak occurring 6 h after stimulation. These results suggest the presence of β2-adrenoceptors in mouse pineal cells and a functional relationship between the adenylyl cyclase system and the regulation of N-acetyltransferase expression. British Journal of Pharmacology (1999) 126, 399–406; doi:10.1038/sj.bjp.0702248