In vitro demonstration of metabolic changes during heat regulation in rats

Abstract

Metabolic changes are descr. in the diaphragms isolated from rats previously maintained in cold or warm environments. In homologous serum as medium, glycogen synthesis from glucose and glucose utilization were increased in the diaphragms of "cold" rats. Glycogenolysis in glucose-free serum was also augmented. No differences in O or acetoacetate utilization were observed between the diaphragms of cold and "warm" rats. Glycogen synthesis and glucose utilization by the abdominal muscle of mice previously exposed to cold were also higher than those of mice maintained at a higher temp. When Krebs-Ringer-phosphate was substituted for homologous serum as medium, glucose utilizations did not differ between the diaphragms of cold and warm rats, and glycogen syntheses differed less. The differences of air temperature to which the rats were exposed were not proportional to the metabolic effect in the diaphragm, which was still observable when rats were maintained at 15 or 20[degree]. Glycogen synthesis was much less in homologous serum when the diaphragms of rats were maintained at 37[degree] rather than at 30[degree], and glycogenolysis was often observed. Glycogenolysis was also observed in diaphragms of rats in which fever had been induced by amphetamine sulphate. Rat-liver slices were capable of synthesizing almost as much glycogen from glucose in serum as in Hastings''s medium. No differences in O2 uptake or in the production of acetoacetate were observed between liver slices from cold and warm rats.