Intestinal Na-P(i) cotransporter adaptation to dietary P(i) content in vitamin D receptor null mice.
Recent studies suggest that vitamin D may play a role in intestinal Na(+)-dependent phosphate transport adaptation to variable levels of dietary P(i). Therefore, the goal of the current study was to assess Na(+)-dependent P(i) cotransport activity in transgenic mice to determine whether vitamin D is an essential mediator of this process. Intestinal brush-border membrane (BBM), Na(+)-dependent P(i) cotransport activity was significantly decreased in vitamin D receptor (VDR) null [VDR (-/-)] mice compared with wild-type (VDR+/+) mice. While intestinal Na-P(i) cotransporter (type IIb) mRNA levels were similar in VDR (-/-) and VDR (+/+) mice, type IIb Na-P(i) cotransporter protein expression was markedly suppressed in VDR (-/-) mice compared with VDR (+/+) mice. Furthermore, Na-P(i) cotransport activity in renal BBM was similar in VDR (-/-) and VDR (+/+) mice, but type IIa Na-P(i) cotransporter protein expression was decreased in VDR (-/-) mice. After administration of a low-P(i) diet, type IIb protein expression was significantly increased in VDR (+/+) and VDR (-/-) mice, and type IIb protein expression was present in the intestinal BBM of VDR (-/-) mice. These data demonstrate that intestinal Na-P(i) cotransport adaptation to a low-P(i) diet occurs independently of vitamin D.
Segawa
Hiroko
H
Department of Nutrition, School of Medicine, Tokushima University, Kuramoto-cho 3, Tokushima City 770-8503, Japan.
Kaneko
Ichiro
I
Yamanaka
Setsuko
S
Ito
Mikiko
M
Kuwahata
Masahi
M
Inoue
Yoshio
Y
Kato
Shigeaki
S
Miyamoto
Ken-ichi
K
D000818:Animals; D004032:Diet; D005786:Gene Expression Regulation; D005838:Genotype; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D008871:Microvilli / Q000502:physiology; D010710:Phosphates / Q000172:deficiency* / Q000378:metabolism*; D016226:Phosphorus, Dietary / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D018167:Receptors, Calcitriol / Q000235:genetics* / Q000502:physiology*; D050608:Sodium-Phosphate Cotransporter Proteins; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D050614:Sodium-Phosphate Cotransporter Proteins, Type IIb; D027981:Symporters / Q000502:physiology*; D014807:Vitamin D / Q000235:genetics / Q000378:metabolism*
D010710:Phosphates; D016226:Phosphorus, Dietary; D018167:Receptors, Calcitriol; C493555:Slc34a1 protein, mouse; C493558:Slc34a2 protein, mouse; D050608:Sodium-Phosphate Cotransporter Proteins; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D050614:Sodium-Phosphate Cotransporter Proteins, Type IIb; D027981:Symporters; D014807:Vitamin D