Role of chloride in angiotensin II-induced salt-sensitive hypertension.

The present study investigated the effect of the anion accompanying sodium on the development of angiotensin II-induced hypertension in rats and the role of the sympathetic nervous system and extracellular fluid volume in its mechanism. Hypertension was induced by intraperitoneal infusion of angiotensin II (125 ng/min) for 12 days via miniosmotic pump. High dietary intake of sodium chloride significantly augmented the angiotensin II-induced hypertension (mean blood pressure on day 13, 165 +/- 6 versus 142 +/- 6 mm Hg, p less than 0.05), but equimolar sodium loading provided as sodium citrate failed to enhance angiotensin II hypertension (140 +/- 6 mm Hg). Plasma norepinephrine concentration in the conscious, resting state increased with sodium chloride loading in angiotensin II-infused rats (594 +/- 42 versus 312 +/- 37 pg/ml, p less than 0.01), but it remained unchanged with sodium citrate loading (324 +/- 23 pg/ml). Correspondingly, maximum response to hexamethonium bromide, a ganglion blocker, was greater in sodium chloride-loaded angiotensin II rats (77.7 +/- 4.6 mm Hg) than that in angiotensin II (59.7 +/- 5.1 mm Hg) or in sodium citrate-loaded angiotensin II (57.7 +/- 4.2 mm Hg) rats. Moreover, extracellular fluid volume, measured as Na2(35)SO4 space, increased in sodium chloride-loaded angiotensin II rats (427 +/- 18 ml/kg body wt) as compared with that in angiotensin II rats (375 +/- 15 ml/kg body wt) but not when compared with volume in sodium citrate-loaded angiotensin II (389 +/- 7 ml/kg body wt) rats.(ABSTRACT TRUNCATED AT 250 WORDS)