Effect of catecholamines on enzyme release from human adipose tissue cells

Effect of adrenaline (A) and noradrenaline (NA) on the release of enzymes were studied in the isolated human adipocytes incubated in Krebs-Hanseleit buffer to which albumins saturated with fatty acids or albumins, from which fatty acids were partly removed, were added. In the incubation fluid the activity of lactic dehydrogenase, malic dehydrogenase, isocitrate dehydrogenase or pyruvate kinase was determined. Besides that, the effects of adrenaline and noradrenaline on the content of non-esterified fatty acids (NEFA) in the adipocytes and on the release of glycerol into the incubation fluid were studied. Both A and NA stimulated the release of all examined enzymes into the incubation medium. The amount of the released enzymes, determined on the basis of changes in their activity in the incubation medium, depended on the degree of albumin saturation with fatty acids. Increased release of enzymes into the incubation fluid was associated with a rise in the content of NEFA in the adipocytes. Gycerol release into the incubation medium was independent of the degree of albumin saturation with fatty acids.