| Autor: |
Wasserman RH; Department of Physiology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853., Chandler JS, Meyer SA, Smith CA, Brindak ME, Fullmer CS, Penniston JT, Kumar R |
| Jazyk: |
angličtina |
| Zdroj: |
The Journal of nutrition [J Nutr] 1992 Mar; Vol. 122 (3 Suppl), pp. 662-71. |
| DOI: |
10.1093/jn/122.suppl_3.662 |
| Abstrakt: |
The intestinal absorption of calcium has been proposed to occur by the transcellular transfer of Ca2+ through the enterocyte proper and between the cells of the intestinal epithelium, i.e., the paracellular path. Attention in this report is given to the transcellular models of Ca2+ absorption and, more specifically, the Ca2+ extrusion events occurring at the basolateral membrane. These extrusion processes include the operation of an ATP-dependent Ca2+ pump and a Na+/Ca2+ exchanger, as well as exocytosis as the terminal event in a proposed vesicular transport mechanism. Evidence for the presence of an ATP-dependent Ca2+ pump at the basolateral membrane is documented and illustrated with biochemical and immunological data from studies on the avian intestinal basolateral membrane. As shown immunohistochemically, the Ca2+ pump was primarily localized on the enterocyte basolateral membrane. The ATP-dependency and vitamin D enhancement of Ca2+ uptake by isolated basolateral membrane vesicles are shown. Western blot analysis of intestinal mucosa, by using a monoclonal antibody produced against the erythrocyte Ca2+ pump, indicated that the number of pump units is increased by 1,25-dihydroxycholecalciferol. The possible involvement of calbindin-D28K as a direct stimulator of the Ca2+ pump is discussed, and the quantitative relationship between Ca2+ transport rates and Ca2+ pumping activity has been estimated. Information related to the basolateral membrane Na+/Ca2+ exchanger and the vesicular transport model of Ca2+ absorption is also briefly reviewed. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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