Neurohumoral factors in borderline hypertension.

Role of neurohumoral factors in borderline hypertension was evaluated in comparison to those in established hypertension. Although there was no significant difference in urinary noradrenaline between the 2 groups, urinary adrenaline was significantly higher in borderline hypertension than in established hypertension. During head-up tilt and Schellong's test a significant increase of diastolic blood pressure was demonstrated in borderline hypertension, whereas a significant decrease of systolic blood pressure was observed without any significant change of diastolic pressure in established hypertension. There was no significant difference in blood pressure response to cold pressor test, plasma volume, total body potassium and plasma renin activity (PRA) between the 2 groups. Blood pressure did not change after administration of captopril in normal subjects but it decreased significantly after captopril in patients with borderline hypertension even when blood pressure became normotensive during hospitalization. Blood pressure decreased significantly after captopril in patients with established hypertension. However, no significant relationship between the pretreatment PRA and the reduction of mean blood pressure was observed in both groups. It can be concluded from the present study that borderline hypertension is intermediate between normal subjects and established hypertension and that both the renin-angiotensin system and the kinin-prostaglandin system play some role in the maintenance of blood pressure in borderline hypertension.