Adrenergic activity and peripheral hemodynamics in relation to sodium sensitivity in patients with essential hypertension.

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Abstract
In 25 outpatients with essential hypertension, Na sensitivity, defined as the difference in mean arterial pressure (.DELTA.MAP) between 2 wk of high-Na (300 mmol/day) and 2 wk of low-Na (LS) intake (50-100 mmol/day), was studied in relation to the plasma norepinephrine (NE) level, NE release and pressor response to i.v. NE. In addition, forearm blood flow (FBF) was measured by plethysmography. There were 2 control periods of regular Na intake, 1 of 4 wk duration at the beginning of the study and 1 of 2 wk duration at the end. The .DELTA.MAP ranged from +18 to -8 mm Hg. The 8 patients in whom .delta.MAP was > 10 mm Hg were regarded as salt-sensitive subjects, salt-sensitive patients had higher plasma NE levels in the control period (P < 0.05) and after 2 wk of HS intake (P < 0.01). Na sensitivity was directly related to the change in plasma NE between the HS and LS periods (P < 0.001). The NE release decreased in salt-insensitive subjects whereas it increased in salt-sensitive patients between the LS and HS periods. Changes in NE release were directly related to Na sensitivity (P < 0.05). The pressor response to NE was not significantly influenced by changes in Na intake. The FBF fell in salt-sensitive patients and increased in salt-insensitive subjects between the LS and HS periods. Na sensitivity was directly related to the change in forearm vascular resistance (P < 0.01). Changes in adrenergic activity and in vascular resistance apparently contribute significantly to Na sensitivity.