Our recent studies utilizing an in vivo regional
ischemia model revealed no changes in the subcellular distribution of
protein kinase C (PKC) in dog and rabbit hearts after repeated 5 min episodes of preconditioning
ischemia/reperfusion. However, 10 min of sustained
ischemia resulted in an increase in PKC activity in the membrane fraction. These findings indicate that prolonged
ischemia may cause changes in the subcellular distribution of PKC. However, the detailed time course of these changes during sustained severe
ischemia is poorly resolved. Thus, our objective was to study temporal changes in PKC distribution in the cytosolic, nuclear, and membrane fractions isolated from globally ischemic rabbit heart. Hearts were removed under deep
anesthesia, placed into
normal saline at 37 degrees C, and repeatedly sampled from apex to base at baseline, 2, 5, and 10 min into global
ischemia, with matched samples obtained in every heart. PKC activity was increased at 2 min into global
ischemia in both the nuclear fraction (1069 +/- 75 vs. 893 +/- 49 pmol/min/g at baseline; p = 0.05) and the membrane fraction (1374 +/- 95 vs 1187 +/- 59 pmol/min/g at baseline; p < 0.05) with persistent translocation observed at 5 and 10 min into the protocol. Thus, direct biochemical determination of PKC activity in the isolated rabbit heart revealed increased activity in the nuclear and the membrane fractions as early
as 2 min into global
ischemia.