DISSOCIATION OF LIPOLYSIS FROM LEVELS OF CYCLIC-AMP IN RAT EPIDIDYMAL FAT-CELLS

  • 1 January 1977
    • journal article
    • research article
    • Vol. 227  (2) , 180-194
Abstract
The relationship between cyclic[c]AMP levels and lipolysis was examined in suspensions of rat epididymal fat cells, using several stimulators of lipolysis. Three inhibitors of lipocyte cAMP phosphodiesterase, theophylline, etazolate hydrochloride (SQ 20009; 1-ethyl-4-(isopropylidenehydrazino)-1H-pyrazolo-(3,4-b)-pyridine-5-carboxylic acid, ethyl ester, hydrochloride) and SQ 20006 (etazolate lacking the isopropylidine moiety) potentiated the stimulation of lipolysis by either epinephrine or cAMP, but only theophylline stimulated lipolysis to maximum levels in the absence of other stimulating agents, even though both pyrazolopyridines were more potent inhibitors of phosphodiesterase than was theophylline. The stimulation of lipolysis by theophylline in the absence of epinephrine occurred with minimal changes in cAMP levels; the stimulation of lipolysis by epinephrine was well correlated with large increases in the level of cAMP. SQ 4665 (8-aza-9-furfuryl-adenine) similarly produced maximum lipolysis in the absence of epinephrine without effecting the levels of cAMP and was approximately 2 orders of magnitude more potent than theophylline in this regard. The presence of a non-cAMP dependent pathway for the stimulation of lipolysis in rat epididymal fat cells.