Selective potentiation of angiotensin-induced constriction of skeletal muscle resistance arteries by chronic elevations in dietary salt intake.

Sprague-Dawley rats were fed either a high-salt (HS, 4.0% NaCl) or a low-salt (LS, 0.4% NaCl) diet for 3 days (short-term) or 4-8 weeks (chronic). Vasoconstrictor responses to angiotensin II and norepinephrine were determined in isolated skeletal muscle resistance arteries and in distal arterioles of the in situ cremaster muscle. Myogenic responses to increases in transmural pressure were also assessed in skeletal muscle resistance arteries of animals on high- or low-salt diets. Chronic (but not short-term) HS diet selectively potentiated angiotensin II-induced constriction of skeletal muscle resistance arteries relative to vessels from LS controls. Myogenic responses and norepinephrine-induced constriction of resistance arteries were unaffected by either chronic or short-term HS diet. Constriction of cremasteric arterioles in response to angiotensin II and norepinephrine was unaffected by chronic or short-term elevations in dietary salt intake. These data suggest that chronic elevations in dietary salt intake lead to a selective increase in the constriction of skeletal muscle resistance arteries to angiotensin II that may allow these vessels to continue to regulate their tone in response to this peptide, despite the suppression of angiotensin II that occurs with high-salt diet. Copyright 1999 Academic Press.