title: Sodium dependence of sodium-proton exchange in platelets from patients with essential hypertension.
abstract: The sodium dependence of recovery of cytoplasmic pH (pHi) after an acid load was studied in platelets from 15 patients with untreated essential hypertension (mean arterial pressure 117 +/- 2.3 mmHg, mean +/- SE) and in 15 normotensive controls (mean arterial pressure 90 +/- 2.2 mmHg). Proton flux was measured in gel-filtered platelets loaded with pH sensitive fluorescent indicator. Sodium dependent proton efflux was prevented by 5 (N,N hexamethylene) amiloride, a potent inhibitor of sodium-proton exchange. The relationship between initial rate of proton efflux and extracellular sodium concentration obeyed Michaelis-Menten kinetics. The maximum initial rate of proton efflux was similar in hypertensive and normotensive subjects (1.93 +/- 0.35 mmol H+1/sec, mean +/- SE, and 1.88 +/- 0.26 mmol H+l/sec respectively). The Michaelis-Menten constant (the sodium concentration at which the initial rate of proton efflux is half maximal) was also similar in the two groups: 75.7 +/- 13.9 mmol/l and 8.15 +/- 10.6 mmol/l respectively. There was no significant correlation between either of these parameters and arterial blood pressure.
authors.affiliation: Department of Clinical Pharmacology, United Medical School, Guy's Hospital, London, UK.
authors.forename: H S
authors.initials: HS
authors.lastname: Doktor
authors.forename: N
authors.initials: N
authors.lastname: Benjamin
authors.forename: S D
authors.initials: SD
authors.lastname: Todd
authors.forename: J M
authors.initials: JM
authors.lastname: Ritter
mesh_terms: D000328:Adult; D000368:Aged; D000643:Ammonium Chloride / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D001798:Blood Proteins / Q000502:physiology; D002352:Carrier Proteins / Q000502:physiology*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006973:Hypertension / Q000097:blood* / Q000503:physiopathology; D008875:Middle Aged; D012964:Sodium / Q000494:pharmacology*; D017923:Sodium-Hydrogen Exchangers
chemical_list: D001798:Blood Proteins; D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D000643:Ammonium Chloride; D012964:Sodium