| Popis: |
Although the close relationship between high blood pressure and obesity has been pointed out in many epidemiologic or clinical studies, the underlying mechanisms of hypertension in overweight patients still remain unclear. The purpose of the present study is to clarify the role of water-sodium balance, sympathetic nerve activity, the renin-angiotensin system and renal dopaminergic activity on the hypertensive mechanisms in overweight patients with essential hypertension （EHT）. In 113 inpatients with mild to moderate essential hypertension receiving a regular diet containing 200mEq of sodium, 75mEq of potassium, 2400Cal/day, there were significant positive correlations between the obesity index （using Minowa's index） and mean arterial pressure （MAP）, plasma volume （PV）, extracellular fluid volume （ECFV）, and total exchangeable sodium （Nae）. MAP, PV, ECFV and Nae were greater in obese EHT than those in non-obese EHT. On the other hand, a significant negative correlation was observed between the obesity index and plasma noradrenaline concentration （pNA） and plasma renin activity （PRA）. The mean values of pNA and PRA in obese EHT were significantly lower than in mildly obese or non-obese EHT. In 41 EHT, following sodium restriction （35mEq of sodium, 75mEq of potassium, 2400Cal/day） for one week, MAP and body weight were significantly decreased and a significant negative correlation was demonstrated between basal obesity index and the changes in MAP and body weight following the procedure. Fractional excretion of sodium （FENa） correlated negatively with the obesity index in obese EHT, unlike in mildly obese or non-obese EHT. The mean value of FENa in obese EHT was significantly lower than that in MAP- and endogenous creatinine clearance （Ccr）-matched mildly obese or non-obese EHT. Following intravenous infusion of dopamine （3μg/kg/min, 60min）, urinary excretion of sodium （UNa V） and FENa significantly increased. This natriuretic response to infused dopamine was significantly greater in obese EHT than in non-obese EHT. In addition, urinary excretion of free dopamine （uDA） was correlated positively with the obesity index in those EHT whose obesity index was less than 15%, but a significant negative correlation was found in patients with an obesity index of 15% or more. These findings suggest that the blunted natriuretic ability, which might be attributed to an ?attenuation of the renal dopaminergic activity, at least in part, may play an important role in the hypertensive mechanisms in obese EHT through the expansion of body fluid volume and sodium. |
