Metabolic-membrane coupling in red blood cells of trout: the effects of anoxia and adrenergic stimulation.

Under oxygenated conditions, in vitro, the highly aerobic red cells of the rainbow trout (Salmo gairdneri) exhibit tight coupling between energy (i.e. nucleotide triphosphate, NTP)-consuming and NTP-producing metabolic activity, as shown by strict maintenance of red cell NTP:haemoglobin ratios. This coupling is maintained following adrenergic stimulation of oxygenated red cells when the increased NTP demands of ion transporting systems are met by enhanced energy production via aerobic metabolism. In unstimulated anoxic red cells, membrane-metabolic coupling is preserved via the arrest of NTP-consuming processes. Adrenergic stimulation of anoxic red cells, however, leads to a functional uncoupling of membrane metabolism with the result that NTP levels decline rapidly. At this time, cellular [NTP] is negatively correlated with [Na+]i and [Cl-]i and positively correlated with [K+]i. This, in addition to the fact that the pH of the intracellular compartment is also highly dependent on cellular NTP levels, provides evidence for the integration of energy and membrane metabolisms.