The effects of age and environmental temperature on the blood concentrations of glucose, free fatty acids and glycerol in new-born rabbits.

1. The concentration of blood glucose, free fatty acids and serum glycerol of the doe, new-born and young rabbits have been measured in order to evaluate the effects of age, starvation and environmental temperature on the circulating concentrations of these metabolites.2. The blood glucose, free fatty acid and glycerol concentrations were lower in the new-born than in the mother rabbit.3. Starvation for 24 hr of new-born and young rabbits in a thermal neutral environment did not alter the serum free fatty acid or glycerol concentrations. The blood glucose of unfed rabbits fell during the first 24 hr of life.4. Cold exposure (15 or 25 degrees C) for 1 hr caused a rise in the concentration of blood glucose, serum free fatty acids and glycerol.5. When the metabolic response of new-born and young rabbits to cold exposure was measured, it was found that there was a direct correlation between the serum glycerol concentration and the metabolic response. The greatest rise in the serum free fatty acids occurred in the blood of rabbits with the poorest metabolic response to cold.6. It is suggested that in the steady state during cold exposure the serum glycerol concentration may indicate the rate of triglyceride hydrolysis in brown adipose tissue.