Effects of exposure to cold and catecholamines on the respiratory quotient and plasma levels of free fatty acids, glucose and urea in rats acclimated to 15 degrees C.

The reported experiments were carried out on 95 male Wistar rats weighing 300 to 360 g kept for 3 weeks in separate cages in a room at an ambient temperature of 15 degrees C. The rats normally fed or fasted for 24 hours were injected at 24-26 degrees C with adrenaline or noradrenaline (400 micrograms/kg s.c.) or injected at 15 degrees C with propranolol (1 mg/kg s.c.). The metabolic rate (MR), respiratory quotient (RQ) and plasma levels of free fatty acids (FFA), glucose (G) and urea (U) were determined. Similarly as in the non-acclimated rats, the determined parameters considered separately were insufficient for estimating the changes in the catabolism of lipids, carbohydrates and proteins, but a simultaneous determination of the RQ and plasma levels of FFA, G or U with MR measurement indicated the degree of lipid, carbohydrate or protein participation in cold-induced thermogenesis.