Ouabain, digitalis-like factors and hypertension

To review the evidence that ouabain and other digitalis-like factors are present in the human circulation under normal circumstances and in various disorders of fluid and electrolyte balance that are associated with hypertension. Recent evidence on a number of ouabain-related issues includes (1) evidence for the existence of inhibitors of sodium pumps in mammalian plasma, (2) the identification of one of these factors as ouabain, (3) measurements of plasma levels of ouabain in man, (4) evidence that ouabain causes chronic hypertension in rats and is associated with human hypertension, and (5) data on some probable mechanisms that may mediate the pressor effect. The available data support the novel hypothesis that ouabain is an endogenous circulating agent in man and other mammals and is likely to influence long-term blood pressure levels.