RYANODINE INDUCED BLOCK OF A CLONED HUMAN CARDIAC POTASSIUM CHANNEL

The effects of ryanodine in a cloned human cardiac potassium channel ( hKvl.S) expressed in a stable mouse L cell line was studied using whol e 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 th e end of a 250 ms pulse. Dose response data fitted to a Hill equation yielded IC50 of 1.2 mu M. The degree of block was not voltage dependen t. Peak current was reduced from 43.6 +/- 12.5% at 10(-5)M to 11.3 +/- 4.8% at 10(-7)M ryanodine. Ryanodine reduced the tail current amplitu de without changing the time course relative to the control. The inhib ition was only partially reversible at concentrations below 10(-6)M. ( C) 1995 Academic Press Limited