Evidence for a hypertensive factor in the blood of essential hypertensives

From plasma of essential hypertensives and normotensives several fractions were obtained after: (1) removing proteins with a relative molecular mass greater than 6,000-8,000, and (2) chromatography on a Biogel P4 or Biogel P2 column. The eluate was separated into 3-4 fractions. These fractions were concentrated to a small volume of 0.5 ml and were injected intravenously in normotensive rats, the mean arterial pressure of which was monitored. One of the fractions from normotensive plasma increased blood pressure in the rat in some but not in all cases. Using the fractions from hypertensive plasma there was an increase in blood pressure in the fraction corresponding to that of normotensive plasma increasing blood pressure and in another fraction of lower molecular weight. Angiotensin II is unlikely to be responsible, since it could be identified in another fraction than that containing the hypertensive factor. It can be concluded that in the blood of essential hypertensives a hypertensive factor is present, which increases blood pressure even in normotensive animals. Its secretion may represent the critical step in the pathogenesis of essential hypertension.