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

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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 ICa 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 ICa 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.
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