Problems in the identification and measurement of a sodium transport inhibitor in human plasma

Circumstantial and direct evidence suggests that human plasma contains an inhibitor or inhibitors of sodium transport and that the level of this inhibitor or inhibitors is raised in many patients with essential hypertension. Although considerable work has been carried out, its exact nature and structure are not as yet known. In order to clarify the issue from a biochemical/methodological point of view, an attempt has been made to illustrate the complexity of the sodium pump and the conceptual and technical problems associated with the identification and measurement of this transport inhibitor in plasma.