EFFECT OF COLD EXPOSURE ON RESPIRATORY C¹⁴O₂PRODUCTION DURING INFUSION OF ALBUMIN-BOUND PALMITATE-1-C¹⁴IN WHITE RATS

Abstract

Albumin palmitate-1-C 14 complex was infused at a constant rate through a carotid cannula (inserted 5–7 days earlier) into otherwise intact non-fasted rats in environments at 30° or 6 °C, after acclimation to 30° or 6 °C. At 6 °C, both warm- and cold-acclimated rats similarly exhaled as C I4 O 2 a larger proportion of the injected C 14 and gave lower terminal amounts of C 14 in the extracted free fatty acids (F.F.A.) of plasma than at 30 °C. These results indicate that plasma F.F.A. serve as substrate for cold-thermogenesis. Also, increased turnover and oxidation of F.F.A. are not always inversely related to carbohydrate utilization but may be increased under conditions which result in concomitantly higher rates of turnover and oxidation of glucose.