Effects of naloxone on cardiac energy metabolism in hypovolemic shock in rats.

It has been reported that naloxone may be useful in the treatment of hypovolemic shock. However, the effects of naloxone on cardiac energy metabolism in hemorrhagic shock have not been investigated. The effects of naloxone on myocardial metabolism were evaluated in the rats which were bled to a systolic pressure of 40 mmHg and maintained at that pressure for 30 min. Naloxone (10 mg/kg) was administered intravenously 5 min before the heart was removed. Then the intramyocardial high energy phosphates, pyruvate, lactate, and glycogen were measured. Naloxone increased systolic blood pressure and decreased heart rate significantly. However, there were no significant differences in high energy phosphates, energy charge, pyruvate, lactate and glycogen between the control and naloxone groups. These data suggest that naloxone may have no direct effect on the cardiac energy metabolism in a 30-min hypovolemic shock.