Improvement of postischemic, contractile function by the calcium channel blocking agent nitrendipine in conscious dogs.

The effect of the new calcium channel blocking agent, nitrendipine, on recovery of contractile function following a 10-min left anterior descending coronary artery occlusion was studied in conscious dogs instrumented with sonomicrometers in the subendocardium of ischemic and normal regions. Nitrendipine (1.0 and 2.5 micrograms/kg/min i.v.) or drug vehicle was administered 30 min prior to the onset of coronary artery occlusion and continued for 30 min following reperfusion accomplished by inflation and deflation of a vascular balloon cuff. Nitrendipine produced a dose-related reduction in arterial pressure and an increase in heart rate and left circumflex coronary blood flow velocity. At 6 h following reperfusion in control dogs (N = 8), segment shortening was significantly reduced from control levels (71 +/- 10% of control). In comparison, dogs pretreated with nitrendipine (3 micrograms/kg/min i.v.) (n = 8) had significantly greater recovery of segment shortening throughout the reperfusion period (102 +/- 10% of control at 6 h following reperfusion). The data demonstrate that pretreatment with the calcium channel blocking agent enhances the recovery of function in postischemic, reperfused, "stunned" myocardium.