Renal haemodynamic and sympathetic responses to head-up tilt in essential hypertension

Abstract

Nine mild-to-moderate hypertensive patients (HT), aged 41±0.6 years (mean± SEM) and nine age-matched normotensive control subjects (NT) were tilted to 60° for 10 min. During tilt, both systolic (S) blood pressure (BP) (p<0.01) and diastolic (D) BP (p<0.05) increased in HT, but not in NT. At supine rest renal blood flow was higher in HT than in NT and increased by 17% in HT during tilt, while a decrease of 13% was observed in NT (p<0.05). Renal vascular resistance was unchanged in HT during tilt, while a significant increase (p<0.01) was observed in NT. Arterial plasma noradrenaline increased in both groups (p<0.05) during tilt, significantly more in HT than in NT (p<0.05) No statistically significant difference was observed between the groups in renal catecholamine uptake or release. Our data indicate enhanced general sympathetic and circulatory responses to tilt in subjects with mild-to-moderate essential hypertension. However, the enhanced haemodynamic and sympathetic responses were not shared by hypertensive kidneys and renovascular resistance remained unaffected by tilt.

Key Words:

• adrenaline
• blood pressure
• catecholamines
• renal blood flow
• noradrenaline