B-3-Adrenoceptor agonist stimulation of the Na ,K -pump in rat skeletal muscle is mediated by beta(2)- rather than beta(3)-adrenoceptors

Abstract

BACKGROUND AND PURPOSE: In cardiac muscle, BRL 37344, a selective beta3-adrenoceptor agonist, activates the Na+, K+ -pump via NO signalling. This study investigated whether BRL 37344 also activates the Na+, K+ -pump via beta3-adrenoceptors in skeletal muscle. EXPERIMENTAL APPROACH: Isolated rat soleus muscles were incubated between 1 and 60 min in buffer. Intracellular Na+, K+ content and Na+, K+ -pump activity were measured using flame photometry and ouabain-suppressible 86Rb+ uptake, respectively. Additional muscles were mounted on force transducers and stimulated (60 Hz for 2 s) every 10 min. KEY RESULTS: BRL 37344 (10(-8) -10(-5) M) induced a concentration- and time-dependent reduction i..