Regulation of intestinal phosphate transport. I. Segmental expression and adaptation to low-P(i) diet of the type IIb Na(+)-P(i) cotransporter in mouse small intestine.
The Na(+)-P(i) cotransporter NaPi-IIb (SLC34A2) has been described to be involved in mouse small intestinal absorption of P(i) and to be regulated by a number of hormones and metabolic factors. However, a possible segmental expression of NaPi-llb in small intestine has not been addressed so far. Here, we describe that the NaPi-IIb cotransporter is highly abundant in the ileum of mouse small intestine, whereas it is almost absent in the duodenum and in the jejunum. Na(+)-P(i) cotransport studies with isolated brush border membranes confirmed that NaPi-IIb cotransport is highest in the ileum. Upregulation by a low-phosphate diet of NaPi-IIb and NaPi-IIb cotransport was observed both in the jejunum and the ileum. Furthermore, evidence is provided that a low-phosphate diet provokes an increase of the NaPi-IIb mRNA abundance along the entire small intestine. These data suggest that in mouse small intestine, phosphate is absorbed transcellulary by an Na(+)-dependent pathway in the ileum, whereas in the duodenum and jejunum, this pathway is of minimal importance. Furthermore, we conclude that along the entire mouse small intestine, low-phosphate diet affects transcription and/or the stability of NaPi-IIb mRNA.
Radanovic
Tamara
T
Institute of Physiology, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
Wagner
Carsten A
CA
Murer
Heini
H
Biber
Jürg
J
D000818:Animals; D015153:Blotting, Western; D004032:Diet; D005455:Fluorescent Antibody Technique; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism*; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D051379:Mice; D008871:Microvilli / Q000378:metabolism; D010710:Phosphates / Q000172:deficiency / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050608:Sodium-Phosphate Cotransporter Proteins; D050614:Sodium-Phosphate Cotransporter Proteins, Type IIb; D027981:Symporters / Q000378:metabolism*; D014158:Transcription, Genetic
D010710:Phosphates; D012333:RNA, Messenger; C493558:Slc34a2 protein, mouse; D050608:Sodium-Phosphate Cotransporter Proteins; D050614:Sodium-Phosphate Cotransporter Proteins, Type IIb; D027981:Symporters