Effect of Nucleic Acid Metabolites on Lipolysis in Adipose Tissue

It has been observed that nucleic acids, nucleotides, and nucleosides inhibit the lipolytic action of epinephrine on adipose tissue, whereas purine and pyrimidine bases increase it (1).Further studies, described in the present report, have shown this interaction to be quite specific for lipolysis (uptake and esterification of fatty acids being unaffected), but not limited to epinephrine (other lipolytic hormones are also inhibited by ribonucleic acid).The chemical nature of this interaction remains undefined, although a number of possibilities can be excluded.Perhaps, fundamental to an understanding of the phenomenon is the distinction (2) between esterification of fatty acids taken up from the medium (not affected by ribonucleic acid) and net re-esterification of acids in the lipolytic pool (increased by ribonucleic acid), EXPERIMENTAL PROCEDURE Materials Nucleic acids, nucleotides, nucleosides, and bases were obtained from Schwarz BioResearch, Inc., and Sigma Chemical Company, and used without further purification.Three different lots of cyclic 3'-5'-AMP' from these two suppliers gave identical results in the present experiments.The ACTH (Lot N 64406) came from Armour and Company; the TSH (Lot 104993), from the California Corporation for Biochemical Research; and glucagon (Lot CT-1116), from Eli Lilly and Company.Palmitic acid-l-Cl4 was obtained from the New England Nuclear Corporation, and Tracerlab, Inc.; the epinephrine-1-Cr4, from the California Corporation for Biochemical Research. MethodsEpididymal fat pads taken from male Sprague-Dawley rats, 250 to 300 g, fed ad libitum, were incubated for 2 or 3 hours in 5 ml of Krebs-Ringer-bicarbonate buffer (3) containing 5% albumin and test reagents (glucose, palmitic acid-1-CY4, lipolytic agents, metabolites, etc.).Before use, the albumin (Armour Fraction V from bovine plasma, prepared for microbiological use) was dissolved in water to make a 10% solution and was clarified by filtration through a Millipore filter (800 mp) .