Nucleated red cell function: metabolism and pH regulation

Abstract

The full extent and apportionment of aerobic and anaerobic contributions to energy transduction for membrane pumps associated with cellular pH regulation are very poorly understood. One way of approaching this problem at the cellular level is by using the nucleated erythrocyte as a model cell. Indeed, the aerobic and anaerobic capacity of salmonid erythrocytes and their β-adrenergic mediated pH regulation offers a model "pH regulating system" for examining cellular strategies of response to acute and (or) chronic changes in oxygen availability. Much of our work has focused on the balance between metabolic energy production and the maintenance of erythrocytic pH through primarily or secondarily active ionic exchange mechanisms at the cell membrane. Upon adrenergic stimulation, a rise in cyclic AMP activates the Na+–H+ exchanger, leading to cell alkalinization and an elevation of intracellular Na+. The increased Na+ evidently stimulates Na+,K+-ATPase activity and the increased ATP consumption is matched with aerobic energy production. The pHi that is subsequently established appears to be set by levels of poly anionic phosphates.