Humoral vasopressor agents in primary hypertension

In essential hypertension and in the spontaneously hypertensive rat, there are indications for a yet unidentified vasopressor agent which may play an important role in pathogenesis. It has been demonstrated in the spontaneously hypertensive rat by parabiosis, cross-circulation, cross-transplantation of kidneys and by injection of hypertensive plasma fractions. In plasma from essential hypertensives, an agent sensitizing the vasculature to pressor hormones and a substance with direct vasopressor actions have been found. The relationship of the hypertensive factor to the natriuretic hormone is not clear.