title: Reduced cytosolic free sodium concentration in vascular smooth muscle cells from spontaneously hypertensive rats.
abstract: 1. Cytosolic free sodium concentration and sodium transport systems were measured in intact cultured vascular smooth muscle cells from spontaneously hypertensive rats of the Münster strain and from normotensive Wistar-Kyoto rats using the sodium-sensitive fluorescent dye sodium-binding benzofuran isophthalate. 2. Resting cytosolic free sodium concentration was significantly lower in vascular smooth muscle cells from spontaneously hypertensive rats than from Wistar-Kyoto rats (10.2 +/- 1.5 mmol/l, n = 26, versus 19.4 +/- 2.5 mmol/l, n = 20, P < 0.01). 3. Inhibition of Na+, K(+)-ATPase by ouabain caused a dose-dependent increase in cytosolic free sodium concentration in spontaneously hypertensive rats and Wistar-Kyoto rats. 4. Activation of Na(+)-Ca2+ exchange by ionomycin increased cytosolic free sodium concentration in both strains. However, the ionomycin-induced increase in cytosolic free sodium concentrations was significantly higher in vascular smooth muscle cells from spontaneously hypertensive rats than from Wistar-Kyoto rats (220 +/- 35% of the resting cytosolic free sodium concentration versus 148 +/- 27%; P < 0.05). The ionomycin-induced increase in cytosolic free sodium concentration was prevented in the absence of external sodium or by inhibition of Na(+)-Ca2+ exchange by NiCl2. 5. Activation of Na(+)-H+ exchange by intracellular acidification of vascular smooth muscle cells with propionic acid increased cytosolic free sodium concentration in each strain (19.6 +/- 5.7 versus 16.3 +/- 3.2 mmol/l). 6. It is concluded that concepts concerning the role of cytosolic free sodium concentration in the pathogenesis of primary hypertension need to be reinvestigated.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Medizinische Universitäts-Poliklinik, University of Münster, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Tepel
authors.forename: J
authors.initials: J
authors.lastname: Holthues
authors.forename: M
authors.initials: M
authors.lastname: Neusser
authors.forename: P
authors.initials: P
authors.lastname: Golinski
authors.forename: Z
authors.initials: Z
authors.lastname: Zhu
authors.forename: N
authors.initials: N
authors.lastname: Mehring
authors.forename: W
authors.initials: W
authors.lastname: Zidek
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006973:Hypertension / Q000378:metabolism*; D015759:Ionomycin / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011422:Propionates / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism*
chemical_list: D011422:Propionates; D015759:Ionomycin; D010042:Ouabain; D012964:Sodium