Primary active sodium transport, oxygen consumption, and ATP: Coupling and regulation

The relationship between active transport at the plasma membrane and respiration has been studied extensively in the kidney, because this organ utilizes a large percentage of energy for this dissipative process. In the kidney, the rate of respiration follows linearly the rate of active transport. Various approaches have explored the coupling between these two variables [for review, 1, 2, 3]. To study this coupling, it has become necessary to investigate the properties of the mitochondria and the active transport systems within the intact cell. This has provided additional challenges not encountered when the mitochondria and the transport enzymes are studied in isolation. Ample evidence indicates that, in general, properties derived from isolated mitochondria and the isolated Na,K-ATPase are also displayed in the intact cell. However, some surprises have been forthcoming because of uncertainties concerning the cellular environment surrounding the mitochondria and transport enzymes.This presentation is divided into the following four parts: cytosolic signal linking active transport with respiration, respiratory capacity of the mitochondria and active transport, differentiation between primary transport and primary metabolic events, and control of transport by metabolism