Figure 5. cAMP-dependent protein kinase (cA-PK) inhibitors antagonise the effects of NO donors on the Iso-stimulated I_Ca,L in rat ventricular myocytes.

A, a myocyte was first dialysed with cA-PK inhibitory peptide (PKI; 20 μm) and exposed to external control solution. Applications of Iso (100 pM, 10 nm) and SNAP (1 nm, 1 μm) are indicated by the lines. Traces were recorded at the times indicated by the corresponding letters on the main graph (a-h). The dotted line indicates the zero-current level. B, summary of the effects of Iso (100 pm), SNAP (1 nm, 1 μm), in myocytes dialysed with PKI (20 μm). C, overview of the effects of Iso (1–100 pm), SNAP (1 nm), in the absence or in the presence of external adenosine-3′,5′-cyclic monophosphothioate, Rp-isomer (Rp-cA 300 μm). The amplitude of I_Ca,L in the presence of agonists was normalised to the amplitude of the basal I_Ca,L in the absence of agonists. Bars are the means and vertical lines are the s.e.m. of the number of experiments indicated near the bars. Significant differences from the Iso (*) or the Iso plus SNAP (#) levels: *P≤ 0.05; #P≤ 0.01.