Figure 4. The role of protein kinases in the forskolin- and isoprenaline-induced increase in I_Kr.

Aa, effect of 3 μM staurosporine on I_Kr tail current amplitude and the effect of forskolin (5 μM) in the continued presence of staurosporine (n = 4). The protein kinase C inhibitor bisindolylmaleimide I (100 nM) completely inhibited the increase in I_Kr induced by forskolin (Ab) and isoprenaline (Ac). Ad, phorbol dibutyrate (100 nM) increased I_Kr tail current amplitude. B, the effect of isoprenaline on I_Kr (upper traces) and I_Ca (lower traces) in the presence of bisindolylmaleimide I (100 nM). I_Kr and I_Ca in B were recorded from the same cells and the arrows indicate 100 pA above zero current in the upper figures and zero current in the lower figures. *P < 0.05.