Hyperresponsiveness of vitamin D receptor gene expression to 1,25-dihydroxyvitamin D3. A new characteristic of genetic hypercalciuric stone-forming rats
| Autor: | David A. Bushinsky, Murray J. Favus, Paru P. Kathpalia, Jianling Yao |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
Calbindins
medicine.medical_specialty Transcription Genetic Duodenum Biology Kidney Calbindin Calcitriol receptor Bone and Bones Bone resorption S100 Calcium Binding Protein G Calcitriol Internal medicine Gene expression medicine Vitamin D and neurology Animals Hypercalciuria RNA Messenger Northern blot Cycloheximide Rats Inbred Strains Sequence Analysis DNA General Medicine medicine.disease Rats Up-Regulation medicine.anatomical_structure Endocrinology Gene Expression Regulation Intestinal Absorption Dactinomycin Receptors Calcitriol Calcium Injections Intraperitoneal Research Article |
| Zdroj: | Journal of Clinical Investigation. 101:2223-2232 |
| ISSN: | 0021-9738 |
| DOI: | 10.1172/jci1164 |
| Popis: | Hypercalciuria in genetic hypercalciuric stone-forming (GHS) rats is accompanied by intestinal Ca hyperabsorption with normal serum 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ) lev- els, elevation of intestinal, kidney, and bone vitamin D re- ceptor (VDR) content, and greater 1,25(OH) 2 D 3 -induced bone resorption in vitro. To test the hypothesis that hyperre- sponsiveness of VDR gene expression to 1,25(OH) 2 D 3 may mediate these observations, male GHS and wild-type Sprague- Dawley normocalciuric control rats were fed a normal Ca diet (0.6% Ca) and received a single intraperitoneal in- jection of either 1,25(OH) 2 D 3 (10-200 ng/100 g body wt) or vehicle. Total RNAs were isolated from both duodenum and kidney cortex, and the VDR and calbindin mRNA levels were determined by Northern blot hybridization using spe- cific cDNA probes. Under basal conditions, VDR mRNA levels in GHS rats were lower in duodenum and higher in kidney compared with wild-type controls. Administration of 1,25(OH) 2 D 3 increased VDR gene expression significantly in GHS but not normocalciuric animals, in a time- and dose-dependent manner. In vivo half-life of VDR mRNA was similar in GHS and control rats in both duodenum and kidney, and was prolonged significantly (from 4-5 to . 8 h) by 1,25(OH) 2 D 3 administration. Neither inhibition of gene transcription by actinomycin D nor inhibition of de novo protein synthesis with cycloheximide blocked the upregula- tion of VDR gene expression stimulated by 1,25(OH) 2 D 3 ad- ministration. No alteration or mutation was detected in the sequence of duodenal VDR mRNA from GHS rats com- pared with wild-type animals. Furthermore, 1,25(OH) 2 D 3 administration also led to an increase in duodenal and renal calbindin mRNA levels in GHS rats, whereas they were ei- ther suppressed or unchanged in wild-type animals. The re- sults suggest that GHS rats hyperrespond to minimal doses of 1,25(OH) 2 D 3 by an upregulation of VDR gene expression. This hyperresponsiveness of GHS rats to 1,25(OH) 2 D 3 ( a ) occurs through an increase in VDR mRNA stability without involving alteration in gene transcription, de novo protein synthesis, or mRNA sequence; and ( b ) is likely of functional significance, and affects VDR-responsive genes in 1,25(OH) 2 D 3 target tissues. This unique characteristic suggests that GHS rats may be susceptible to minimal fluctuations in serum 1,25(OH) 2 D 3 , resulting in increased VDR and VDR-respon- sive events, which in turn may pathologically amplify the actions of 1,25(OH) 2 D 3 on Ca metabolism that thus contrib- ute to the hypercalciuria and stone formation. ( J. Clin. In- vest. 1998. 101:2223-2232.) Key words: vitamin D receptor • gene expressionrat • 1,25(OH) 2 D 3 • hypercalciuria |
| Databáze: | OpenAIRE |
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