Postischemic Changes in Cardiac Sarcoplasmic Reticulum Ca 2+ Channels

Abstract

We investigated the modifications of cardiac ryanodine receptors/sarcoplasmic reticulum Ca2+ release channels occurring in ischemic preconditioning. In an isolated rat heart model, the injury produced by 30 minutes of global ischemia was reduced by preexposure to three 3-minute periods of global ischemia (preconditioning ischemia). The protection was still present 120 minutes after preconditioning ischemia but disappeared after 240 minutes. Three 1-minute periods of global ischemia did not provide any protection. In the crude homogenate obtained from ventricular myocardium, the density of [3H]ryanodine binding sites averaged 372±18 fmol/mg of protein in the control condition, decreased 5 minutes after preconditioning ischemia (290±15 fmol/mg, P<.01), was still significantly reduced after 120 minutes (298±17 fmol/mg, P<.05), and recovered after 240 minutes (341±21 fmol/mg). Three 1-minute periods of ischemia did not produce any change in ryanodine binding. The Kd for ryanodine (1.5±0.3 nmol/L) was...