title: Reduced intestinal epithelial cell brush border membrane calcium transport in spontaneously hypertensive rats.
abstract: OBJECTIVE
  The present study aimed to determine whether there were alterations in intestinal calcium homeostasis in the spontaneously hypertensive rats (SHR) and to identify at which interface of the intestinal epithelial cell (brush border or basolateral) this occurs.
  
  
  METHODS
  Controversy exists as to whether intestinal calcium transport is altered in association with hypertension. Studies using perfused duodenal segments of the SHR have shed little light on the problem; other studies have only measured calcium transport in brush border membrane vesicles. This study allows specific focus on calcium transport mechanisms at both the brush border and basolateral membrane using simultaneously prepared membrane vesicles.
  
  
  METHODS
  Calcium transport was studied by measuring radiolabelled calcium (45Ca) uptake in isolated brush border and basolateral membrane vesicles, prepared from the small intestines of SHR and Wistar-Kyoto (WKY) rats. Calcium uptake was measured when vesicles were incubated in solutions containing different concentrations of ATP and calcium. Orientation and membrane marker assays were used to confirm the phenotypes of the two membrane vesicle preparations.
  
  
  RESULTS
  ATP-dependent calcium efflux was only observed in the basolateral membrane, which contains the Ca2+ -ATPase pump. SHR brush border membrane vesicles displayed no significant increase in calcium incorporation, whereas WKY brush border vesicles showed a 500% increase in uptake (ANOVA, P<0.05, n = 7).
  
  
  CONCLUSIONS
  This study indicates that deficiencies exist in SHR intestinal calcium transport at the brush border membrane of intestinal epithelial cells. While further studies are required to ascertain the exact mechanisms involved, postulated deficiencies in the actions of calcium regulating hormones at this membrane suggest the need for concurrent intake of a calcitrophic agent to assist calcium uptake at the brush border membrane.
authors.affiliation: Department of Physiology, The University of Melbourne, Parkville, Australia.
authors.forename: T E
authors.initials: TE
authors.lastname: de Gooyer
authors.forename: W
authors.initials: W
authors.lastname: Farrugia
authors.forename: M E
authors.initials: ME
authors.lastname: Wlodek
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D006973:Hypertension / Q000378:metabolism* / Q000473:pathology; D007413:Intestinal Mucosa / Q000378:metabolism*; D007421:Intestine, Small / Q000378:metabolism / Q000473:pathology; D017136:Ion Transport; D008871:Microvilli / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
chemical_list: D002132:Calcium Radioisotopes; D000255:Adenosine Triphosphate; D002118:Calcium