Fig. 3. The activities of mito-μ-calpain during ischemia-reperfusion.
Panel A: the activity of mito-μ-calpain is significantly increased in mouse heart mitochondria following ischemia-reperfusion compared to time control. The calpain inhibitor MDL effectively prevents mito-μ-calpain activation during ischemia-reperfusion.
Panel B: immunoblotting shows that ischemia and reperfusion does not alter the protein content of mito-μ-calpain compared to time control [Mean ± SEM: time control 1.12 ± 0.18 (Arbitrary unit, n=4); ISC-REP, 0.90 ± 0.03 (n=4); p=NS vs. IR]. Calpastatin is an endogenous inhibitor of calpain. Ischemia-reperfusion also does not alter the content of calpastatin localized within mitochondria [Mean ± SEM: time control 1.07 ± 0.33 (Arbitrary unit, n=4); IR, 0.96 ± 0.08 (n=4); p=NS vs. IR], suggesting that the increased mito-μ-calpain activity is not due to the loss of its endogenous inhibitor during ischemia-reperfusion. Subunit 4 of cytochrome oxidase (COX) is used as the loading control. Data are expressed as mean ± SEM; * p<0.05 vs. time control, † p<0.05 vs. untreated hearts.