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 responses during coronary bolus perfusion, as in coronary angiography, in three species and related the responses to the bolus content of electrolytes and to patterns of cardiac electrolyte regulation. METHODS. Isolated, paced hearts from the rat, guinea pig, and rabbit were subjected to coronary perfusion in the global mode with recording of left ventricular 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 the 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 negative 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 and rate of the sarcomal Na-Ca exchange. In series 2 of the experiments, iohexol (150 mg I/mL) +/- minor electrolyte additives were studied. Additives with Na 30 mmol/L only or with Na, Ca, K, and Mg carefully balanced reduced positive and negative inotropic responses in all three species.