Linked Life Data

1836238

Source:http://linkedlifedata.com/resource/pubmed/id/1836238

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
22
pubmed:dateCreated
1992-1-22
pubmed:abstractText
The thymidine analogues 5-bromo-2'-deoxyuridine (Brd-Urd) and 5-iodo-2'-deoxyuridine (IdUrd) compete with thymidine for incorporation into the DNA of replicating cells. This incorporation results in radiosensitizing effects which are directly related to the degree of analogue substitution. In vitro and in vivo evidence suggests that preadministration or coadministration of the thymidylate synthetase inhibitors fluorouracil and 5-fluoro-2'-deoxyuridine (FdUrd) can modulate analogue incorporation into DNA. We have evaluated in the rabbit VX2 tumor model the effects of thymidylate synthetase inhibitor (fluorouracil or FdUrd) coadministration (as 24-hour, intravenous infusions) on the incorporation of BrdUrd or IdUrd into the DNA of relevant normal tissues (bone marrow, gut mucosa) and intrahepatic VX2 tumor. Tissues were harvested and processed for gas chromatography-mass spectrometry analysis of the thymine, 5-bromouracil, and 5-iodouracil contents in hydrolyzed DNA. Coadministration of FdUrd resulted in statistically significant (P less than .01) enhancement of IdUrd incorporation into the DNA of intrahepatic VX2 tumor and normal (bone marrow and duodenal mucosa) rabbit tissues. Coadministered fluorouracil, on the other hand, significantly enhanced IdUrd incorporation only into DNA of intrahepatic VX2 tumor. Statistically significant enhancement of BrdUrd incorporation was achieved only with FdUrd coadministration and then only into the DNA of intrahepatic VX2 tumor. The percent of thymine replaced by analogue (I) is related to the steady-state arterial plasma drug concentration (C) by the Michaelis-Menten equation: I = I(MAX.) C/(C50 + C). The primary effect of FdUrd coadministration on BrdUrd incorporation into VX2 tumor DNA was a reduction of the C50 parameter (plasma BrdUrd concentration eliciting I = I(MAX)/2) from 8.17 microM to 1.78 microM. On the other hand, the I(MAX) parameter (I as C approaches infinity) was only slightly affected (29.7% to 25.2%). Thus, the degree to which the modulator enhanced analogue incorporation varied inversely with the analogue's steady-state plasma concentration. These results, which describe potential tissue specificity of modulator efficacy and characterize the effects of thymidylate synthetase inhibitor modulation on thymidine analogue incorporation pharmacodynamics, should provide guidance as to dose scheduling of BrdUrd and IdUrd in clinical trials for improved tumor specificity of uptake.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0027-8874
pubmed:author
pubmed:issnType
Print
pubmed:day
20
pubmed:volume
83
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1659-67
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
Biochemical modulation of 5-bromo-2'-deoxyuridine and 5-iodo-2'-deoxyuridine incorporation into DNA in VX2 tumor-bearing rabbits.
pubmed:affiliation
Upjohn Center for Clinical Pharmacology, University of Michigan School of Medicine, Ann Arbor 48109.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.