Ryanodine induced block of a cloned human cardiac potassium channel

The effects of ryanodine in a cloned human cardiac potassium channel (hKv1.5) expressed in a stable mouse L cell line was studied using whole cell voltage clamp technique. Ryanodine in a dose dependent manner (10−7−10−5 M) reduced the peak current as well as the current at the end of a 250 ms pulse. Dose response data fitted to a Hill equation yielded IC50 of 1.2 μ . The degree of block was not voltage dependent. Peak current was reduced from 43.6 ± 12.5% at 10−5 to 11.3 ± 4.8% at 10−7 ryanodine. Ryanodine reduced the tail current amplitude without changing the time course relative to the control. The inhibition was only partially reversible at concentrations below 10−6 .