Regulation of the 25-hydroxyvitamin D₃ 1 alpha hydroxylase and 24-hydroxylase gene promoters.

Abstract

1,25(OH)2D3, plays important roles in many process such as calcium homeostasis. The vitamin D hydroxylase enzymes, vitamin D l-hydroxylase (La(OH)ase) and vitamin D 24-hydroxylase (CYP24) are the key rate limiting enzymes responsible for the bioaotivation and degradation of 1,25(OH)2rD3, respectively. Several physiological factors including PTH, 1,25(OH)2rD3 , and calcitonin interact to regulate the gene expression of the two enzymes resulting in regulation of serum and tissue levels of 1,25(OH)2rD3. The aim of the study in this thesis was to understand the molecular mechanism by which PTH regulates expression of the human 1a(OH)ase gene promoter in the kidney and also the molecular mechanisms by which 1,25(OH)2rD3 and calcitonin regulate expression of the rat CYP24 promoter in kidney and osteoblast cells.