Growth hormone stimulation of lipolysis and cyclic AMP levels in perifused fat cells

K Sengupta, KJ Long and DO Allen

A rapid, sustained lipolytic response to growth hormone (GH; 20 microgram/ml) was observed in experiments using the perifused fat cell system. No lipolytic response to this agent was observed when fat cells were incubated by the traditional flask incubation method, although isoproterenol stimulated lipolysis in this preparation. In experiments using flask incubated fat cells, isoproterenol increased cyclic AMP content while GH had no effect. However, in the presence of theophylline, isoproterenol and GH significantly increased cyclic AMP levels. In perifused fat cells, both isoproterenol and GH significantly increased cyclic AMP levels in the absence of theophylline. The presence of adenosine deaminase resulted in significant increases in the lipolytic response to isoproterenol and unmasked a lipolytic response to GH when the flask-incubated fat cell system was used. The antilipolytic action of adenosine was determined in perifused fat cells. It was found that the lipolytic response to GH was at least 10 times as sensitive to the inhibitory action of adenosine as was the lipolytic response to isoproterenol. It is concluded that the lipolytic response to GH in the flask-incubation method is prevented by the accumulation of adenosine. This rapid lipolytic response is unmasked in the perifused fat cell system because adenosine fails to accumulate as it is washed from the cell population by the constantly flowing buffer.

Volume 217, Issue 1, pp. 15-19, 04/01/1981
Copyright © 1981 by American Society for Pharmacology and Experimental Therapeutics