The concept of the natriuretic hormone and its relation to hypertension.

Acute volume expansion increases the intrathoracic blood volume thus endowing the plasma with an increased capacity to cause a natriuresis, to inhibit Na-K-ATPase and stimulate vascular reactivity. It is not known whether these changes, which stem from a common stimulus are due to a change in the concentration of one substance or several. It is proposed that in essential hypertension a genetic abnormality of the kidney causes a difficulty in excreting sodium. This leads to an initial blood volume expansion which causes the observed rise in the plasma's capacity to inhibit sodium transport, and to the increased vascular tone. Eventually the increase in tone of the arterial smooth muscle causes the blood pressure to rise, while the increase in tone of the smooth muscle of the veins diminishes venous compliance thus causing a shift of blood from the periphery to the chest thus providing the stimulus for the persistent rise in the plasma's capacity to increase vascular reactivity, even though total blood volume may have returned to normal.