本態性高血圧症の昇圧機序における交感神経系の意義 ―特に血漿Noradrenaline濃度に対する加齢と腎Noradrenaline Clearanceの影響―
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The present study was conducted to elucidate the role of sympathetic nerve activity related to ageing in the pressor mechanism of essential hypertension. In 83 hospital-admitted patients with mild to moderate essential hypertension (EHT) and 126 normotensive subjects (NT) receiving a regular diet containing 200mEq of sodium and 75mEq of potassium daily, there was a significant positive correlation between plasma noradrenaline concentration (pNA) at supine rest and age in NT, but not in EHT. Mean value of pNA in young (less than 40 years old) subjects was significantly higher in EHT than that in NT, unlike in the middle-aged (40-59 years old) and old-aged (over 60 years old) groups. On the other hand, a significant positive correlation or a similar tendency was observed between pNA and both mean arterial pressure (MAP) and heart rate (HR) in NT and EHT. This relationship between pNA and MAP was not presented in any age groups of NT, but was pronounced in the young EHT, weak in the middle-aged EHT, and disappeared in the old-aged EHT. No significant relation was found between pNA and HR in any aged-groups of either NT or EHT. Following 60° head-up tilt for 20 minutes (tilt), MAP increased in young and middle-aged NT and young EHT, whereas it remained unchanged in old-aged NT, and decreared in middle-aged and old aged EHT. PNA and HR significantly increased in the three age groups both in NT and EHT. Change in MAP during tilt correlated negatively with age both in NT and EHT. Tilting induced pNA elevation in NT and EHT, but tended to be lower in the middle- and old-aged groups than in the young groups. In EHT, pNA correlated positively with plasma renin activity (PRA) and negatively with plasma volume (PV), extracellular fluid volume (ECFV) and exchangeable sodium (Nae). The regression line between pNA and PRA shifted downward with ageing. On the other hand, a negative correlation between pNA and PV, ECFV and Nae in EHT was demonstrated only in the young group. The mean value of renal clearance of noradrenaline (CNA) in EHT was highest in the young, second highest in the middle-aged and lowest in the old-aged groups. In addition, CNA correlated negatively with age and pNA in EHT. These results suggest that the sympathetic nerve activity estimated by pNA levels is closely ?related to the renin-angiotensin system and water-sodium balance, and the enhanced activity may play an important role in the pressor mechanism of EHT, particularly in young EHT. In addition, attenuated renal noradrenaline clearance was demonstrated in the old-aged EHT, suggesting that much caution may be required if sympathetic nerve activity is evaluated only by pNA levels in elderly EHT.
- 1990-08-01
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