Calcium uptake into enterocyte brush-border membrane vesicles is greater in spontaneously hypertensive than in normotensive control rats.
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.
Hennessen
U
U
Inserm Unité 90, Départment de Néphrologie, Hôpital Necker, Paris, France.
Comte
L
L
Steuf
M C
MC
Lacour
B
B
Drüeke
T
T
McCarron
D A
DA
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
D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium