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Intestinal Na-P i cotransporter adaptation to dietary P i content in vitamin D receptor null mice

2004; American Physical Society; Volume: 287; Issue: 1 Linguagem: Inglês

10.1152/ajprenal.00375.2003

1931-857X

Hiroko Segawa, Ichiro Kaneko, Setsuko Yamanaka, Mikiko Ito, Masahi Kuwahata, Yoshio Inoue, Shigeaki Kato, Ken–ichi Miyamoto,

Ion Transport and Channel Regulation

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.