title: Effects of dietary salt on angiotensin peptides in kidney.
abstract: This study used a novel simple method for the extraction, separation, identification, and quantitation of angiotensin-like immunoactivity from tissue to examine the effects of altering dietary NaCl intake on intrarenal angiotensin I, II, and III levels in salt-sensitive, spontaneously hypertensive rats, salt-resistant Wistar-Kyoto rats, and Sprague-Dawley rats. Seven-week-old male spontaneously hypertensive rats, Wistar-Kyoto rats, and Sprague-Dawley rats were assigned randomly to a diet containing either 8% (high) or 1% (basal) salt and were maintained on these diets for 3 wk. Rats were then decapitated without prior anesthesia, and kidneys were rapidly (< 30 s) removed, snap frozen in liquid nitrogen, and stored at -80 degrees C. Frozen tissue was extracted in 2 M acetic acid and then subjected to solid-phase extraction with the cation exchange resin AG 50W X4. Angiotensin peptides were separated by reversed-phase high-performance liquid chromatography on a phenyl silica gel column with an eluent consisting of 20% acetonitrile in 0.1 M ammonium phosphate buffer, pH 4.9, and quantitated by radioimmunoassay. The elution of standard peptides under isocratic conditions revealed clear resolution of angiotensin I, II, and III and the (1-7) and (3-8) peptides. Recoveries of both labeled and unlabeled angiotensin peptide standards from the extraction step were > 90%. Renal angiotensin II stores were significantly higher in spontaneously hypertensive rats than in Wistar-Kyoto or Sprague-Dawley rats, independent of diet. Renal angiotensin II and III were further suppressed during dietary salt supplementation in both salt-resistant strains but not in the spontaneously hypertensive rat. These findings are consistent with an enhanced (compared with Wistar-Kyoto and Sprague-Dawley rats) role for angiotensin II in the kidney of the salt-sensitive, spontaneously hypertensive rat, particularly under conditions of dietary salt supplementation.
authors.affiliation: Department of Medicine, University of Alabama at Birmingham, USA.
authors.forename: Q C
authors.initials: QC
authors.lastname: Meng
authors.forename: J
authors.initials: J
authors.lastname: Durand
authors.forename: Y F
authors.initials: YF
authors.lastname: Chen
authors.forename: S
authors.initials: S
authors.lastname: Oparil
mesh_terms: D000803:Angiotensin I / Q000378:metabolism*; D000804:Angiotensin II / Q000378:metabolism*; D000805:Angiotensin III / Q000378:metabolism*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004039:Diet, Sodium-Restricted; D004351:Drug Resistance; D007668:Kidney / Q000378:metabolism*; D008297:Male; D010446:Peptide Fragments / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017207:Rats, Sprague-Dawley; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D010446:Peptide Fragments; D000804:Angiotensin II; D000805:Angiotensin III; D012965:Sodium Chloride; D000803:Angiotensin I