Rates of Turnover, Recycle and Oxidation of Blood Glucose on Cold Exposure in Sheep

The glucose metabolism of sheep under the constant environmental temperatures of 20°C and 0°C was measured by isotope dilution method with the single injection and the constant infusion of 14C- and 3Hlabelled glucose.In the environmental temperature of 20°C, the pool size, turnover rate, re-cycling rate of glucose and the percentage of CO2 derived from glucose to the total expired CO2 were 159.5 mg/kg, 2.63 mg/min/kg, 0.40 mg/min/kg and 5.37%, respectively.On the 4th day after the exposure to 0°C, the values of pool size, turnover rate, re-cycling rate and CO2 percentage derived from glucose were increased to 1.67 (226.0 mg/kg), 1.86 (4.88 mg/min/kg), 2.93 (1.17 mg/ min/kg) and 2.23 (12.0%) times high compared with those of 20°C.These results indicated that the sheep which scarecely absorbs glucose from the alimentary tracts synthesize glucose by gluconeogenesis and utilize it with the same rate as the monogastric animal. Under the cold environment, the turnover rate of glucose increased remarkably to be used to quite a large extent as the sources for the heat production.