Calcium uptake by duodenal enterocytes isolated from young and mature SHR and WKY rats: influence of dietary calcium
Roullet, C.M.; Young, E.W.; Roullet, J.B.; Lacour, B.; Drüeke, T.; McCarron, D.A.
American Journal of Physiology 257(4 Pt 2): F574-F579
1989
ISSN/ISBN: 0002-9513 PMID: 2801960 Document Number: 332502
Intestinal calcium (Ca2+) transport was examined at the cellular level using duodenal enterocytes isolated from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Compartmental analysis of 45Ca2+ uptake was performed on enterocytes isolated from young (12- to 14-wk-old) and mature animals (24- to 26-wk-old) fed either normal (1%) or high (2%) calcium diets. Intracellular Ca2+ flux (Jc) was reduced in SHR compared with WKY for both young (0.67 .+-. 0.05 vs. 1.08 .+-. 0.08 nmol Ca2+.cntdot.mg protein-1.cntdot.min-1 P < 0.01) and mature (0.39 .+-. 0.03 vs 0.71 .+-. 0.05 nmol Ca2+.cntdot. mg protein-1.cntdot.min-1; P < 0.001) animals on a normal calcium diet. On a high-calcium diet, this strain difference of Jc disappeared in the young rats (0.87 .+-. 0.09 vs. 1.06 .+-. 0.06 nmol Ca2+.cntdot.mg protein-1.cntdot.min-1, NS). In mature SHR, the high-calcium diet stimulated Jc, whereas it lowered it in mature WKY resulting in a similar flux for both strains (0.56 .+-. 0.05 vs. 0.49 .+-. 0.05 nmol Ca2+.cntdot.mg protein-1.cntdot.min-1, NS). Young SHR had a lower intracellular Ca2+ pool compared with WKY. This defect was corrected by a high-calcium diet. The membrane Ca2+ flux (Jm) was lower in mature SHR than WKY fed a normal calcium diet (P < 0.02); Jm increased to the control value (P < 0.05) in the SHR on a high-calcium diet. Diet-induced changes of plasma 1,25(OH)2 vitamin D levels in the SHR did not parallel the observed changes of intestinal Ca2+ fluxes. Thus duodenal enterocytes from SHR appear to have an intrinsic alteration of Ca2+ transport that can be corrected in part by a higher calcium diet.