A radioisotopic method for the measurement of free fatty acid turnover and adrenoceptor response in small fragments of human adipose tissue.
New techniques for measuring rates of triglyceride hydrolysis and the re-esterification of resultant free fatty acids (FFA) in small fragments of human adipose tissue are described. Buffered medium containing [14C]-glucose and [3H]-palmitate of high specific activity is used to label newly synthesized acylglycerides in incubated tissue. 14C is incorporated only into the glyceride 'back bone' of acylglycerides, and the rate of incorporation may be used as a measure of the rate of synthesis of each glyceride molecular species. Due to mixing of exogenous [3H]-palmitate with endogenously released FFA, the actual specific activity of FFA esterified to [14C]-glycerides is always less than that of the [3H]-palmitate in the medium. The degree of dilution of [3H]-palmitate with unlabelled FFA is directly proportional to the rate of lipolysis. Thus, determination of the 14C/3H ratio in newly synthesized triglycerides permits the assessment of adrenoceptor dose-response characteristics (lipolysis) of unweighed fragments of adipose tissue. If rates of 14C-tri- and diglyceride accumulation are measured in tissue fragments whose cellularity and rate of glycerol release has been determined, the fraction of newly lipolyzed FFA which are re-esterified can be calculated. This 'cycle' of re-esterification controls the ratio of FFA: glycerol leaving the adipocyte. These techniques can be applied to serial subcutaneous adipose tissue samples from awake subjects in various clinical and experimental states.
D000273:Adipose Tissue / Q000378:metabolism*; D002250:Carbon Radioisotopes; D005215:Fasting; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D005989:Glycerides / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D007553:Isotope Labeling / Q000379:methods*; D008066:Lipolysis / Q000187:drug effects; D008433:Mathematics; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D011941:Receptors, Adrenergic / Q000378:metabolism*; D013806:Theophylline / Q000494:pharmacology; D014316:Tritium
D002250:Carbon Radioisotopes; D005230:Fatty Acids, Nonesterified; D005989:Glycerides; D010169:Palmitic Acids; D011941:Receptors, Adrenergic; D014316:Tritium; D019308:Palmitic Acid; D013806:Theophylline; D005947:Glucose; D007545:Isoproterenol