Metabolic effects of (-)-isoprenaline stimulation of adenylate cyclase in reticulocytes

The metabolic effects of (-)-isoprenaline or/and isobutylmethylxanthine on reticulocyte enriched suspensions of rabbit blood cells and on reticulocyte rich blood of rats were studied. There was no detectable influence of beta-agonist stimulation or/and cyclic nucleotide phosphodiesterase inhibition on total as well as coupled oxygen consumption. However, under the same conditions more than twofold increases of lactate formation were found accompanied by great accumulation of cyclic AMP. These effects are specific and rapid. The peak of lactate production at 5 to 7.5 min was followed by a sharp decline and slow further decrease, whereas cAMP accumulation reached a plateau after 10 to 15 min. A 45% decrease of ATP concentration was found in rat, but not in rabbit reticulocytes. The increased lactate production unaccompanied by changes of oxygen consumption is probably an isolated response of the cytosolic energy producing system. The increased glycolytic rate is probably the consequence of an activation of phosphofructokinase by cAMP. In reticulocyte rich blood of rats, decrease of ATP is a contributing factor of phosphofructokinase activation. The mechanism(s) of dissociation between energy-producing and consuming processes in rat reticulocytes remains unclear.