CONTRACTILE RESPONSES TO ELECTROLYTE CHANGES DURING CORONARY BOLUS PERFUSION - A COMPARATIVE-STUDY IN ISOLATED RAT, GUINEA-PIG, AND RABBIT HEARTS

RATIONALE AND OBJECTIVES. The authors studied cardiac contractile resp onses during coronary bolus perfusion, as in coronary angiography, in three species and related the responses to the bolus content of electr olytes and to patterns of cardiac electrolyte regulation. METHODS. Iso lated, paced hearts from the rat, guinea pig, and rabbit were subjecte d to coronary perfusion in the global mode with recording of left vent ricular developed pressure during exposure (<7.5 seconds) and recovery (30 seconds). RESULTS. In series 1 of the experiments, the perfusate reduction to one fifth of normal Ca, Na, K, Mg, and Ca/Na/K/Mg, and th e removal of all ions, led to the following percentage changes in left ventricular developed pressure: rat -64, +84, -38, +7, +40, and +79; guinea pig -43, +48, +18, +5, +28, and +37; and rabbit -32, +60, +14, +4, +22, and +33. CONCLUSIONS. Except for K reduction, inducing negati ve inotropy in the rat but positive inotropy in the guinea pig and the rabbit, the three species responded similarly. Thus, changes in left ventricular developed pressure were related to changes in direction an d rate of the sarcomal Na-Ca exchange. In series 2 of the experiments, iohexol (150 mg I/mL) +/- minor electrolyte additives were studied. A dditives with Na 30 mmol/L only or with Na, Ca, K, and Mg carefully ba lanced reduced positive and negative inotropic responses in all three species.