Vitamin D is hydroxylated to form several active metabolites, of these, 1,25- dihydroxyvitamin D3 [1,25(OH)2D3] is the most studied stimulatory product. It is now accepted that 1,25(OH)2D3 mediates its rapid actions on the control of phosphate homeostasis through its membrane receptor 1,25D3-MARRS (membrane associated rapid response steroid binding) protein. Another metabolite, 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] has been reported to be inhibitory with respect to calcium and phosphate absorption in intestine. Previous work in this laboratory has indicated that 24,25(OH)2D3 inhibits phosphate uptake in isolated intestinal cells and perfused duodenal loops and in vivo. This thesis further tested the hypothesis that the actions of 24,25(OH)2D3 on phosphate homeostasis are physiologically important. Catalase has been identified as a binding protein for 24,25(OH)2D3. We determined the localization of catalase in the presence and absence of steroid, monitored catalase mRNA levels related to gene 24,25(OH)2D3 gene transcription regulation. We studied the effects of the two isomers of 24,25(OH)2D3 on localization of catalase in chicken enterocytes over a time course of 15 sec to 60 min. It was demonstrated that 24R,25(OH)2D3 is the effective metabolite for catalase redistribution in vitro. We also studied the effects of vitamin D on catalase and phosphate uptake in chicken intestinal cells. It was once again demonstrated that 24R,25(OH)2D3 is the effective metabolite for decreasing phosphate uptake and catalase gene expression. These combined results lead us to conclude that 24,25(OH)2D3 is an important hormone in phosphate homeostasis in chick intestinal epithelial cells.
| Identifer | oai:union.ndltd.org:UTAHS/oai:digitalcommons.usu.edu:etd-5577 |
| Date | 01 May 2015 |
| Creators | Zhang, Yang |
| Publisher | DigitalCommons@USU |
| Source Sets | Utah State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | All Graduate Theses and Dissertations |
| Rights | Copyright for this work is held by the author. Transmission or reproduction of materials protected by copyright beyond that allowed by fair use requires the written permission of the copyright owners. Works not in the public domain cannot be commercially exploited without permission of the copyright owner. Responsibility for any use rests exclusively with the user. For more information contact Andrew Wesolek (andrew.wesolek@usu.edu). |
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