NaCl Induces Differential Changes of Regional Vascular Reactivity in Salt-Sensitive Versus Salt-Resistant Men

Abstract

The objective of our study was to determine the structural or functional factors which increase forearm vascular resistance (FAVR) during a high NaCl diet in salt-sensitive (SS) volunteers. We studied the effects of 20 v 200 mEq/day NaCl diets on FAVR responses to norepinephrine (NE), angiotensin II (AII), nitroprusside, verapamil, and ischemia in 27 men. Twelve men had supine mean arterial pressure (MAP) on high NaCl which was greater than or equal to 5% above MAP on low NaCl and were consequently labeled SS. Eleven subjects had lower MAP on the high NaCl diet and were classified salt-resistant (SR). Basal FAVR was greater in SS (P less than .005) and unchanged in SR subjects on high (v low) NaCl. FAVR responses to NE and nitroprusside were not different between the two diets within either the SS or SR subgroups. FAVR responses to AII decreased during high NaCl in the SR (P less than .01), but not in the SS subset. The response to phentolamine and verapamil increased in SS (P less than or equal to .05) and tended to decrease in SR subjects (P less than .15) during high NaCl. In contrast, the vasodilator response to ischemia was impaired in the SS (P = .02) and enhanced in the SR (P = .02) group on high v low NaCl. Enhanced alpha-adrenergic and Ca2+ channel (verapamil)-dependent vascular tone probably contribute to the greater baseline FAVR in SS subjects on high NaCl. Failure to decrease vasoconstrictor responses to AII may indirectly contribute to their maladjustment of FAVR.(ABSTRACT TRUNCATED AT 250 WORDS)