Maturation-dependent changes of the rat reticulocyte energy metabolism and hormonal responsiveness

Significant reduction of total and coupled respiration as well as an increase of uncoupled respiration characterize the maturation of rat reticulocytes. ATP declines by 45%, whereas ADP increases by 70% and the ATP/ADP ratio decreases from 7.6 to 3.3. At the same time the oxygen-delivery capacity of red blood cells increases by 37% due to an increase of 2.3-BPG level. In the youngest reticulocytes the basic level of cAMP is 2-fold higher, whereas the maximal (-)-isoproterenol-induced accumulation of cAMP is 8-fold higher than in the fraction of most mature reticulocytes. Evidence for the presence of functionally active glucagon-receptors in reticulocytes is presented, with maturational inactivation/disappearance of R2-glucagon receptors.