Multifunctional Ca2+/calmodulin-dependent protein kinase mediates Ca(2+)-induced enhancement of the L-type Ca2+ current in rabbit ventricular myocytes.

The intracellular mechanism underlying the Ca(2+)-induced enhancement of the L-type Ca2+ current (ICa) was examined in adult rabbit cardiac ventricular myocytes by using patch-clamp methodology. Internal Ca2+ was elevated by flash photolysis of the Ca2+ chelator Nitr 5, and intracellular Ca2+ levels were simultaneously monitored by Fluo 3 fluorescence. Flash photolysis of Nitr 5 produced a rapid (< 1-second) elevation of internal Ca2+, which led to enhancement (39% to 51% above control) of the peak inward Ca2+ current after a delay of 20 to 120 seconds.