The effects of anti-anginal drugs on the contraction of the blood-perfused canine papillary muscle under ischemia or non-ischemic hypoxia.

Abstract

The isolated canine papillary muscle (PM) was perfused with blood through the anterior septal artery at a constant pressure of 100 mmHg and was stimulated at 1.5 Hz. The perfusion pressure was decreased to 40 mmHg (ischemia, IS), while in nonischemic hypoxia (NIHY), PM was perfused with the coronary sinus blood (CSB) or with the deoxygenated venous blood (DVB) by a membrane oxygenator (SciMed). PO2 (mmHg), PCO2 (mmHg) and pH were 17±1, 31±1 and 7.37±0.01 in CSB and 21±2, 24±2 and 7.39±0.01 in DVB, respectively. Drugs were injected into the anterior septal artery. The blood flow to PM changed to about 38, 200 and 260 % of the control in IS, NIHY with DVB, and NIHY with CSB, respectively. The contractile force (CF), ±dT/dt and time to peak tension did not change in IS and in NIHY with DVB, but. decreased significantly in NIHY with CSB. The maximum responsive frequency without alternative response decreased in IS or NIHY. Negative inotropic effects (NIE) of verapamil (1-30 μg) tended to be potentiated in IS and in NIHY with DVB and was significantly potentiated in NIHY with CSB. NIE of nifedipine (0.1-3 μg) was not influenced in IS or NIHY. Nitroglycerin (0.3-10 μg) had little effect on CF in these conditions. These results suggest that the decrease in P02alone does not affect CF of PM and that verapamil may exert more potent NIE in ischemic areas of the heart than in normal.