Evidence Using Human Arterial Tissue for a Circulating Vascular Sensitizing Agent in Essential Hypertension*

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Abstract
We studied the effect of plasma from 12 patients With essential hypertensionand 12 normotensive subjects on the contractile response to norepinephrine in human isolated arterial spiral strips. Human mesenteric and uterine arteries were obtained during abdominal surgery; they were cut into spiral strips and set up in isolated organ baths. After the equilibration period, arterial strips were incubated for 20 min in plasma from either normotensive subjects or hypertensive patients, and the contractile responses to norepinephrine (2.96 × 10–7 M) were recorded. Plasma from hypertensive subjects significantly increased the contractile response to norepinephrine by 25.8% (P <0.02). Plasma from normotensive subjects did not increase the contractile response to the pressor agent (–3.2%; P = NS). The mean change in contractile response to norepinephrine in the presence of plasma from hypertensive patients was significantly higher than that after incubation of the human arterial strips in plasma from normotensive subjects (P <0.02). When both groups were considered as a whole, there was a significant correlation between diastolic pressure and the change in the contractile response to norepinephrine (r = 0.52; P <0.01). These results suggest the existence of a. circulating vascular sensitizing substance in patients with essential hypertension.