The protein-specific phosphatase 1 antagonizes the ?-adrenergic increase of the cardiac Ca current

Abstract

In isolated ventricular cells from the adult guinea pig heart the slow Ca current was recorded during β-adrenergic stimulation and during cell dialysis with a protein-specific phosphatase-1 (PPase-1). The increase in the amplitude of I_Ca during bath application of isoprenaline (5×10⁻⁸M) could be completely reversed by dialysing the cell with 2 μM PPase-1. Lower enzyme concentrations produced smaller effects. The control amplitude of I_Ca was only little affected by dialysis with PPase-1. The result suggests 1) that PPase-1 is a likely candidate for the downregulation of Ca channels, 2) that Ca channels can open in the dephosphorylated state.