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Low levels of intestinal calbindin-D28K in X-linked hypophosphatemic mice
Abstract:
Using our radioimmunoassay for chick intestinal calbindin-D28K, a protein homologous to that in the chick intestine on the basis of immuno-crossreactivity, molecular weight and charge properties was identified in mouse intestinal mucosa. No such protein, however, was found in the kidney, cerebellum, cerebrum, liver or myocardium of the mice. In X-linked hypophosphatemic mice (Hyp mice) maintained on a standard diet containing vitamin D, the basal level of intestinal calbindin-D28K was much lower (average 65.13 +/- 7.39%) than that in breeding pairs of normal mice maintained under the same conditions. Although the mean intestinal level of calbindin-D28K was as low as 118.23 +/- 20.08 (SD) ng/mg protein in vitamin D-deficient mice (-D), the level of this protein was markedly increased to the control level (198.68 +/- 9.98 vs. 198.49 +/- 14.29 ng/mg protein of control) (P less than 0.001) in response to the administration of vitamin D3 (1000 I.U. s.c. for 10 days) (+D). These results indicate that calbindin-D28K, biochemically indistinguishable from the chick intestinal calbindin-D28K, is present in the mouse intestine, and that the lower amount of this protein in the Hyp mouse intestine may, at least in part, be responsible for the resistance to the effects of vitamin D.
Insights
Mouse intestinal calbindin-D28K, a vitamin D-dependent protein, is present in the intestine but not other organs. Lower levels in hypophosphatemic mice may contribute to vitamin D resistance.
Area of Science:
- Biochemistry
- Molecular Biology
- Endocrinology
Background:
- Calbindin-D28K is a vitamin D-dependent calcium-binding protein.
- Its presence and role in mammalian intestines, particularly in relation to vitamin D metabolism, are of interest.
Purpose of the Study:
- To identify and characterize calbindin-D28K in mouse intestine.
- To investigate the levels of intestinal calbindin-D28K in X-linked hypophosphatemic mice (Hyp mice) and its regulation by vitamin D.
Main Methods:
- Radioimmunoassay (RIA) using chick intestinal calbindin-D28K antibody.
- Analysis of protein expression in various mouse tissues.
- Assessment of calbindin-D28K levels in vitamin D-deficient and vitamin D-treated Hyp mice.
Main Results:
- Mouse intestinal calbindin-D28K was identified and found to be biochemically similar to chick calbindin-D28K.
- The protein was exclusively detected in the intestinal mucosa, not in kidney, brain, liver, or heart.
- Hyp mice exhibited significantly lower basal levels of intestinal calbindin-D28K compared to normal mice.
- Vitamin D3 administration normalized calbindin-D28K levels in vitamin D-deficient mice.
Conclusions:
- Calbindin-D28K is present in the mouse intestine and its expression is vitamin D-dependent.
- Reduced intestinal calbindin-D28K levels in Hyp mice may contribute to their vitamin D resistance.