Haemodynamic effects of ionophore (X-537A) in cats.

The effects of ionophore X-537A in the doses of 0.5, 1, 2 and 3 mg/kg were studied on the blood pressure, heart rate, left ventricular contractility, cardiac output, cardiac index, left ventricular work index and systemic vascular resistance in open-chest anaesthetized cats. This compound increased the contractility significantly for 15, 60, 120 and 30 min in the doses of 0.5, 1, 2 and 3 mg/kg respectively. A dose of 0.5 mg/kg was ineffective in raising the blood pressure. Doses of 1, 2 and 3 mg/kg, however, raised the blood pressure significantly for 60, 60 and 15 min respectively. There was an increase in the heart rate, but significant only with doses of 1 and 2 mg/kg. Cardiac output, cardiac index, left ventricular work index and systemic vascular resistance did not change significantly with 0.5 mg/kg of X-537A. Doses of 1 and 2 mg/kg increased the cardiac output, cardiac index, left ventricular work index and total systemic vascular resistance for a variable period of time. A dose of 3 mg/kg of ionophore produced a decrease in the cardiac output, cardiac index, and left ventricular work index, and an increase in the total systemic vascular resistance and cardiac contractility for variable periods. Most of the cardiac effects did not last for more than 1 hr, and repeated administration had no effect on cardiovascular function.