Summary of studies of changes in vascular reactivity caused by natriuretic hormones

Endogenous Na, K pump inhibitors may contribute to the pathogenesis of hypertension, and could do so by causing direct vasoconstriction and/or enhancing sensitivity to other vasoconstrictor agents. These effects of the Na, K pump inhibitors are likely due to inhibition of Na-K-ATPase. In turn, cells become depolarized, internal sodium concentration increases and internal calcium is increased by exchange for sodium via the sodium/calcium exchange carrier. This extra calcium is sequestered, increasing the size of the releasable intracellular calcium pool. Both depolarization and the increase in cytosolic calcium can cause vasoconstriction. Both depolarization and the increased size the intracellular calcium pool can sensitize the blood vessel to other vasoconstrictor agents. Endogenous pump inhibitors may also stimulate the release of catecholamines from the intramural sympathetic nerve terminals. Studies of a variety of candidate endogenous Na, K pump inhibitors are reviewed. These include presently unidentified substances extracted from human urine, from peritoneal dialysate of hypertensives with renal failure, and from bovine and rat hypothalamus. Additional candidate compounds include ouabain, selected pregnanes and marinobufagenin, a steroid originally identified in the venom of the frog, Bufo marinus.