Further studies on the existence of a sensitizing factor to pressor agents in hypertension

Further studies are reported on the existence of a sensitizing factor in plasma of hypertensive subjects, which increases the vascular sensitivity to pressor agents when injected iv into nephrectomized rats. Plasma samples from normotensive subjects, patients with malignant hypertension, normotensive dogs, and dogs with experimental renovascular hypertension were fractionated on Bio-Gel P-10 columns after cold acetone precipitation, and on DEAE-cellulose columns eluted with sodium chloride and pH gradients. The effect of the various fractions on the vascular sensitivity to angiotensin was tested utilizing nephrectomized rats. The sensitizing activity was found only in fractions obtained from plasma of hypertensive patients and dogs and it was concentrated primarily in three fractions. Th results suggest that the sensitizing factor is negatively charged at neutral pH and it could be a polypeptide or a small protein.