Effects of sodium butyrate on 1,25-dihydroxyvitamin D3 receptor activity in primary chick kidney cells.

The genomic effects of the steroid hormone 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) are mediated by high affinity nuclear associated specific receptors that belong to the superfamily of ligand induced transcription factors. The carboxylic acid, sodium butyrate--a potent inhibitor of histone deacetylase--is known to modulate gene expression in a variety of systems. Specific binding of 1,25(OH)2D3 to its receptor was examined in primary chick kidney cells, the chick macrophage cell line HD-11, and other mammalian cell lines such as ROS 17/2.8, HT-29 and CV-1 cells, that were all cultured in the presence or absence of 1 mM sodium butyrate. Treatment with n-butyrate resulted in significant (4.0-4.5-fold) increases in 1,25(OH)2D3 receptor binding without changing binding affinity only in the primary cultures of chick renal epithelial cells and the chick macrophage cell line but not in the other heterologous receptor-positive cell lines. The maximum increase in receptor binding was evident at 1 mM butyrate concentration. This effect reached a maximum at 15 h treatment, beyond which there was slow attenuation in increased binding until 24 h. The butyrate induced increases in receptor activity was associated with increases in the 1,25(OH)2D3-mediated induction of calbindin-D28K protein only in primary chick kidney cultures but not in the macrophage cell line (HD-11). Similarly, calbindin-D28K promoter activity was enhanced only in butyrate-treated primary chick kidney cultures, transfected with chimeric plasmids containing the 5' flanking sequence of the calbindin-D28K promoter fused to the chloramphenicol acetyl transferase (CAT) reporter gene but not in HD-11 cells.(ABSTRACT TRUNCATED AT 250 WORDS)