Calcium uptake kinetics into brush-border membrane vesicles: higher Vmax in the spontaneously hypertensive rat than in normotensive control.
Arterial hypertension in the spontaneously hypertensive rat (SHR) is associated with an abnormal Ca2+ homeostasis, compared with its normotensive control, the Wistar Kyoto rat (WKY). In particular, epithelial Ca2+ transport is perturbed, with intestinal absorption and renal tubular reabsorption being decreased in the adolescent and adult SHR. In the present study we examined Ca2+ uptake into isolated duodenal brush-border membrane vesicles (BBMV) in 12-14 week-old male rats. This uptake can be separated in a nonsaturable and a saturable component. The latter follows Michaelis-Menten kinetics. Vmax of this component was found to be significantly higher (p less than 0.05) in SHR than in WKY (0.58 +/- 0.19 versus 0.35 +/- 0.06 nmol/mg protein x 10 sec, mean +/- SD) whereas Km did not differ. Thus, the defect in the intestinal Ca2+ absorption previously identified in the SHR of this age is not due to a decrease in Ca uptake at the level of the duodenal brush-border membrane, but is most likely located in the baso-lateral membrane.
Hennessen
U
U
INSERM U90, Hôpital Necker, Paris, France.
Drüeke
T
T
Comte
L
L
Steuf
M C
MC
McCarron
D A
DA
Lacour
B
B
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004386:Duodenum / Q000187:drug effects / Q000378:metabolism*; D006706:Homeostasis; D006973:Hypertension / Q000378:metabolism*; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium