Effects of magnesium orotate on rat heart function.

Female Sprague-Dawley rats were given magnesium orotate (100 mg/kg/day) by gavage for 7 days. The effects on left ventricular, right ventricular, and circulatory function were measured using Millar ultraminiature catheter pressure transducers and thermodilution. In another series, rats were pretreated for 4 days with magnesium orotate. Then they received an intravenous infusion of norepinephrine (0.2 mg/kg/h) for 3 days while magnesium orotate treatment was continued. Thereafter, left ventricular function was examined. Magnesium orotate given for 7 days in control rats induced an increase in heart rate from 380 +/- 18 (n = 7) to 415 +/- 9 beats/min (n = 8); in left ventricular systolic pressure from 165 +/- 8 to 183 +/- 10 mmHg; in left ventricular dP/dtmax from 11486 +/- 1082 to 13300 +/- 909 mmHg/s; and in cardiac output from 386 +/- 38 to 429 +/- 16 ml/kg/min. The pressure-rate product was significantly elevated by magnesium orotate from 54956 +/- 4260 to 66094 +/- 3703 mmHg/min (p < 0.05). Right ventricular systolic pressure was also significantly increased from 34 +/- 1 to 41 +/- 3 mmHg (p < 0.05), and right ventricular dP/dtmax was increased from 2233 +/- 167 to 2857 +/- 489 mmHg/s. Infusion of norepinephrine for 3 days induced an increase in heart rate by 34%, in left ventricular systolic pressure by 10%, in left ventricular dP/dtmax by 88%, in right ventricular systolic pressure by 147%, and in right ventricular dP/dtmax by 100%. Magnesium orotate treatment did not significantly affect the changes induced by norepinephrine.(ABSTRACT TRUNCATED AT 250 WORDS)