Effects of intravenous amino acids on anesthesia-induced hypothermia in ovariectomized rats

A decrease in core temperature during general anesthesia is attenuated by infusion of an intravenous amino acid mixture. The purpose of the present study was to investigate the influence of physical and endocrine changes caused by ovariectomy on the inhibitory effect of amino acid infusion on anesthesia-induced hypothermia. Sprague-Dawley female rats were divided into a sham-operated (Sham) group and an ovariectomized (OVX) group. Saline solution or an amino acid mixture solution was infused for 180 min during sevoflurane anesthesia, and the rectal temperature was measured (4 groups). Intraperitoneal white adipose tissue mass, bilateral gastrocnemius weight and plasma insulin levels were measured. In the Sham rats, no inhibitory effect of the amino acid mixture on anesthesia-induced hypothermia was found, while in the OVX rats, hypothermia was significantly decreased. The intraperitoneal fat weight/body weight ratio was significantly higher in the OVX rats than in the Sham rats, but the gastrocnemius weight/body weight ratio was not significantly different. After amino acid infusion, the plasma insulin level was significantly higher in the OVX rats than in the Sham rats. In conclusion, our findings suggest that, in rats, ovarian function or female hormone affects protein turnover mediated by increase in insulin secretion and, thus, decreases the inhibitory effect of an infusion of amino acid mixture on anesthesia-induced hypothermia.