These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Renal and intestinal calcium transport: roles of vitamin D and vitamin D-dependent calcium binding proteins.
    Author: Johnson JA, Kumar R.
    Journal: Semin Nephrol; 1994 Mar; 14(2):119-28. PubMed ID: 8177979.
    Abstract:
    A model has been presented here for vitamin D-dependent Ca transport, based on observations of the intestinal Ca absorption process. In this model of vitamin D-dependent Ca transport, processes that occur in different areas of the intestinal epithelial cell combine to result in active transport of Ca2+ from the intestinal lumen to the bloodstream. At the brush-border membrane, 1,25(OH)2D3 causes a rapid opening of Ca2+ channels and transport of Ca2+ into the cell in a matter of seconds to minutes by a process that is independent of gene transcription. Inside the cell, 1,25(OH)2D3 stimulates transcription of the CaBP-D9k/28k mRNA and protein in 1 or more hours after 1,25(OH)2D3 treatment. The CaBP-D9k/28k has greater affinity for Ca2+ than do the brush-border membrane components, so Ca2+ movement through the cytosol is facilitated, with Ca2+ carried by CaBP-D9k/28k. At the BLM, 1,25(OH)2D3 causes an increase in concentration of the PMCA, and stimulates Ca(2+)-pumping activity. The PMCA has still greater affinity for Ca2+ than does the CaBP-D9k/28k. The combination of these vitamin D-dependent events results in active transport of Ca across the intestinal epithelia. Vitamin D sufficiency is necessary for this response to vitamin D treatment. This model may apply to renal DT cells as well as to intestinal absorptive cells. Vitamin D-regulated factors that are involved in vitamin D-dependent active Ca transport and are present in both renal DT and intestinal epithelial cells include VDR, CaBP-D9k/28k and the PMCA. The PMCA is localized to the BLM in both cell types. Both kidney and intestine respond similarly to changes in vitamin D, Ca, or P status. The many similarities between renal DT cells and intestinal epithelia strongly support the application of this model for vitamin D-dependent Ca transport in both tissues.
    [Abstract] [Full Text] [Related] [New Search]