Premium
Intestinal phosphate absorption and the effect of vitamin D: a comparison of rats with mice
Author(s) -
Marks Joanne,
Srai Surjit K.,
Biber Jürg,
Murer Heini,
Unwin Robert J.,
Debnam Edward S.
Publication year - 2006
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2005.032516
Subject(s) - ileum , jejunum , small intestine , duodenum , phosphate , medicine , endocrinology , cotransporter , absorption (acoustics) , biology , chemistry , biochemistry , sodium , materials science , organic chemistry , composite material
Previously, it was thought that intestinal phosphate transport occurred exclusively in the proximal small intestine of rodents and humans. However, a recent study has demonstrated that the ileum of mice contributes significantly to the absorption of dietary phosphate, but it is not known whether this region is also an important site of phosphate absorption in the rat. In the present study, we have investigated the mRNA and protein levels of the sodium–phosphate cotransporter, NaPi‐IIb, in three regions of rat and mouse small intestine, and related its expression levels to the rate of net phosphate absorption, as measured using the in situ intestinal loop technique. 1,25‐Dihydroxyvitamin D 3 is an important physiological regulator of intestinal phosphate absorption that increases phosphate transport in both the duodenum and jejunum of the rat. Based on the recently proposed regional profile of phosphate absorption along the mouse small intestine, we have re‐evaluated the effects of 1,25‐dihydroxyvitamin D 3 using three distinct regions of the mouse and rat small intestine. Our studies have revealed important differences in the intestinal handling of phosphate between mice and rats. In mice, maximal phosphate absorption occurs in the ileum, which is paralleled by the highest expression levels of NaPi‐IIb mRNA and protein. In contrast, in rats maximal absorption occurs in the duodenum with very little absorption occurring in the ileum, which is similar to the pattern reported in humans. However, in both rodent species only the jejunum shows an increase in phosphate absorption in response to treatment with 1,25‐dihydroxyvitamin D 3 .