OBJECTIVETo study the effect of zinc deficiency on the protein expression of vitamin D receptor (VDR) and calcium binding protein (CaBP) in growth-term rats duodenal mucosa and to clarify the mechanism of zinc deficiency affecting the calcium absorption by gene transcription.

METHODSThirty weaning male rats were randomly divided into three groups: zinc deficiency (ZD), paired-fed (PF) and zinc adequation (ZA). The ZA group received a diet containing 29.5 microg/g diet ad libitum; the ZD group received a diet containing less than 0.4 microg zinc/g diet ad libitum. To eliminate the effect of zinc deficiency on appetite, the PF group received a zinc-adequate diet restricted to the quantity of food consumed the previous day by the ZD rats. After 15 days feeding, duodenal mucosa was taken to measure expression of the protein of VDR and of CaBP by immunohistochemistry and Western-blotting.

RESULTSImmunohistochemistry demonstrated that the intestinal mucosal expression of both VDR protein and CaBP protein in ZD rats significantly decreased. Analysis of the photographs showed that the number of cells expressed VDR protein in ZD rats was significantly less than that of the PF and ZA rats (P < 0.001). The number of cells which expressed VDR protein in ZD, PF, and ZA groups was 52, 162, and 220, and the number of cells which expressed CaBP protein was 169, 240 and 280 (F = 132 and 22, P < 0.001). Western-blotting showed similar results.

CONCLUSIONSZinc deficiency, by changing the activity of VDR, changes the protein expression of VDR, and thus affects the transcription of the target gene CaBP, resulting in the absorption of calcium that causes allo-osteogenesis.