title: Calcium uptake into enterocyte brush-border membrane vesicles is greater in spontaneously hypertensive than in normotensive control rats.
abstract: Arterial hypertension in the SHR is associated with disturbances of calcium homeostasis, compared with its normotensive control, the WKY. In order to study intestinal Ca2+ handling at the subcellular level, we examined 45Ca2+ uptake kinetics in isolated brush-border membrane vesicles (BBMV). Experiments were conducted in male, 12- to 14-week-old rats on a 1% Ca diet. BBMV were purified by the method of Forstner et al. No difference in BBMV enrichment was observed between SHR and WKY. Ca2+ uptake was studied at various Ca2+ concentrations in the incubation medium (0.025-1.0 mM) and could be separated into a nonsaturable and a saturable component. The saturable component followed Michaelis-Menten kinetics. Vmax in the SHR was greater than in the WKY: 0.576 +/- 0.186 (n = 6) vs. 0.346 +/- 0.10 nmol/mg protein x 10 s (n = 6), mean +/- SD, p less than 0.05. However, Km was not different in the two animal strains. In conclusion, mediated Ca2+ transport into duodenal BBMV was increased in the adolescent SHR. When considering that the transcellular duodenal Ca2+ flux is decreased in the SHR at this age, the rate-limiting step of perturbed transeptithelial Ca2+ transport is probably localized at the site of the basolateral membrane.
authors.affiliation: Inserm Unité 90, Départment de Néphrologie, Hôpital Necker, Paris, France.
authors.forename: U
authors.initials: U
authors.lastname: Hennessen
authors.forename: L
authors.initials: L
authors.lastname: Comte
authors.forename: M C
authors.initials: MC
authors.lastname: Steuf
authors.forename: B
authors.initials: B
authors.lastname: Lacour
authors.forename: T
authors.initials: T
authors.lastname: Drüeke
authors.forename: D A
authors.initials: DA
authors.lastname: McCarron
mesh_terms: D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D004386:Duodenum / Q000378:metabolism*; D006973:Hypertension / Q000378:metabolism*; D008297:Male; D008871:Microvilli / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis
chemical_list: D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium