Ischemic and
reperfusion injuries to the myocardium were evaluated by measuring cardiac function and the
calcium binding capacity of the sarcoplasmic reticulum (SR) and by studying the myocardial protective effect of
nicorandil. While undergoing
cardiopulmonary bypass, dogs were subjected to 120-min global
myocardial ischemia and then to 120-min reperfusion. Group I hearts were arrested with untreated
potassium cardioplegic solution; Group II with the same
solution containing 2 mg/L and Group III with the same plus 10 mg/L of
nicorandil. Group III exhibited better recovery from ischemic and
reperfusion injuries than Group I with recovery rates of LV dp/dt max (95.0 +/- 28.9% vs 61.1 +/- 30.4, p less than 0.05) and LV negative dp/dt max (69.0 +/- 12.5% vs 46.8 +/- 21.7, p less than 0.05). The 3 groups showed a marked decrease in the max
calcium binding capacity during
ischemia compared with the Control Group but exhibited no further decrease after reperfusion. After
ischemia and reperfusion, Group III (30.4 +/- 9.13 nmol Ca/mg
protein, 30.0 +/- 8.50) demonstrated a significantly higher binding capacity than Group I (17.0 +/- 2.41 and 18.3 +/- 1.01, p less than 0.05), while Group II did not. These results suggest that
ischemia is more injurious to the
calcium binding capacity of SR than reperfusion and that 10 mg/L of
nicorandil added to the
cardioplegic solution preserves SR function and enhances the recovery of cardiac function.