Cold effects in rat: plasma and adipose tissue free fatty acids and adipose lipase

¹ Department of Pharmacology, State University of New York, Upstate Medical Center, Syracuse, New York

Male albino rats were exposed to cold or kept at room temperature for 1–24 hr. Plasmas and epididymal adipose tissues were analyzed for free fatty acid (FFA) concentrations and lipolytic activities of intact sections and homogenates, as well as release of FFA by adipose tissues, determined in vitro. Plasmas of rats exposed to cold had significantly higher FFA levels than did plasmas from controls, and intact epididymal adipose tissue sections from cold-exposed rats had higher FFA concentrations, released greater quantities of FFA, and manifested higher lipase activities in the presence of activated triglyceride substrate than did sections from control rats. Exposure to cold may increase FFA mobilization from adipose tissues as a result of enhanced lipolytic activity, due to lipase activation by catecholamines released from adrenals and sympathetic nerve endings. The enzyme activated did not possess several of the properties characteristic of lipoprotein lipase. Tissue homogenates did not manifest increased activity after cold exposure, possibly as a result of activation by the homogenization process itself.