Effect of cold ambient temperature on glucose and alanine turnover in dogs

The metabolic effects of acute cold exposure were examined in dogs exposed to either +25 degrees C (TaN) or -21 degrees C (TaC). Simultaneous infusion of D-3-3H glucose and U-14C alanine was used to measure glucose (R Glu) and alanine carbon (R Ala) turnover rates. At the two ambient temperatures the animals remained normothermic and normoglycemic throughout the experiments. Cold exposure provoked a significant increase in VO2 (X 4.5), plasma 3-hydroxybutyrate concentration (X 1.8), R Glu (X 2.3) and alanine metabolic clearance (X 1.7), while plasma alanine concentration (X 0.4) and R Ala (X 0.6) were significantly decreased. At TaN and TaC, significant direct relationships were found between R (Ala) and plasma alanine concentration, the alanine fractional turnover rate being higher at TaC than at TaN. At the two ambient temperatures, inverse relationship was found between R (Ala) and plasma 3-hydroxybutyrate concentration. These experiments indicate that in spite of increased glucose needs, acute cold exposure is accompanied by reduced alanine release. They suggest that alanine plays only a minor role in cold-stimulated gluconeogenesis in dogs.