Linked Life Data

2847656

Source:http://linkedlifedata.com/resource/pubmed/id/2847656

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1988-11-30
pubmed:abstractText
A pathway has been described in the skin for the synthesis of 24-dehydrovitamin D3 (delta 24D3) from 24-dehydroprovitamin D3. The physiologic function of delta 24D3 is unknown, but has been proposed as a potential inhibitor of hepatic vitamin D-25-hydroxylase. We validated an assay for vitamin D-25-hydroxylase in rat hepatic microsomes, using nanomolar amounts of [3H]D3 as substrate, and found that delta 24D3 competitively inhibits vitamin D-25-hydroxylase activity. The apparent Ki was approximately 17 nM, indistinguishable from the Km of approximately 15 nM, suggesting that both delta 24D3 and cholecalciferol have similar affinity for the enzyme. We found no [3H]delta 24D3 in serum or liver extracts after repletion of vitamin D-depleted rats with [3H]vitamin D3 for 4 h or 6 days. A dose of 1 microgram delta 24D3 to vitamin D- and calcium-depleted rats was unable to promote any elevation in the 45Ca transport by everted duodenal sacs or to increase levels of plasma calcium: thus no evidence for biological conversion of delta 24D3 to vitamin D3 was observed. Further studies are needed to determine whether delta 24D3 is released from the skin to the circulation and is taken up by the liver, before physiological relevance can be attributed to this inhibitor.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0003-9861
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
266
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
532-8
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1988
pubmed:articleTitle
24-Dehydrovitamin D is potent inhibitor of rat liver microsomal vitamin D-25-hydroxylase.
pubmed:affiliation
Department of Medicine, University of Chicago, Illinois 60637.
pubmed:publicationType
Journal Article, In Vitro, Research Support, U.S. Gov't, P.H.S.