Dietary calcium deficiency increases Ca2+ uptake and Ca2+ extrusion mechanisms in chick enterocytes.
Ca2+ uptake and Ca2+ extrusion mechanisms were studied in enterocytes with different degree of differentiation from chicks adapted to a low Ca2+ diet as compared to animals fed a normal diet. Chicks adapted to a low Ca2+ diet presented hypocalcemia, hypophosphatemia and increased serum 1,25(OH)2D3 and Ca2+ absorption. Low Ca2+ diet increased the alkaline phosphatase (AP) activity, independently of the cellular maturation, but it did not alter gamma-glutamyl-transpeptidase activity. Ca2+ uptake, Ca2+-ATPase and Na(+)/Ca2+ exchanger activities and expressions were increased by the mineral-deficient diet either in mature or immature enterocytes. Western blots analysis shows that vitamin D receptor (VDR) expression was much higher in crypt cells than in mature cells. Low Ca2+ diet decreased the number of vitamin D receptor units in both kinds of cells. In conclusion, changes in Ca2+ uptake and Ca2+ extrusion mechanisms in the enterocytes by a low Ca2+ diet appear to be a result of enhanced serum levels of 1,25(OH)2D3, which would promote cellular differentiation producing cells more efficient to express vitamin D dependent genes required for Ca2+ absorption.
Centeno
Viviana A
VA
Laboratorio de Metabolismo Fosfocálcico y Vitamina D "Dr. F. Cañas", Cátedra de Bioquímica y Biología Molecular, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Argentina.
Díaz de Barboza
Gabriela E
GE
Marchionatti
Ana M
AM
Alisio
Arturo E
AE
Dallorso
Maria E
ME
Nasif
Renée
R
Tolosa de Talamoni
Nori G
NG
D000469:Alkaline Phosphatase / Q000378:metabolism; D000821:Animal Feed; D000818:Animals; D015153:Blotting, Western; D002117:Calcitriol / Q000378:metabolism; D002118:Calcium / Q000172:deficiency* / Q000378:metabolism*; D002136:Calcium, Dietary / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002454:Cell Differentiation; D002642:Chick Embryo; D002645:Chickens; D004386:Duodenum / Q000378:metabolism; D020895:Enterocytes / Q000378:metabolism*; D015151:Immunoblotting; D007425:Intracellular Membranes / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000378:metabolism; D019831:Sodium-Calcium Exchanger; D013997:Time Factors; D014807:Vitamin D / Q000378:metabolism; D005723:gamma-Glutamyltransferase / Q000378:metabolism
D002136:Calcium, Dietary; D018167:Receptors, Calcitriol; D019831:Sodium-Calcium Exchanger; D014807:Vitamin D; D005723:gamma-Glutamyltransferase; D000469:Alkaline Phosphatase; D000252:Calcium-Transporting ATPases; D002117:Calcitriol; D002118:Calcium