Linked Life Data

2251676

Source:http://linkedlifedata.com/resource/pubmed/id/2251676

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1991-1-17
pubmed:abstractText
The mechanism by which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) treatment decreases testosterone (T) secretion without significantly altering plasma luteinizing hormone (LH) concentrations was investigated. Testes from sexually mature Sprague-Dawley rats dosed 7 days earlier with 100 micrograms TCDD/kg secreted 30-75% less T than did testes from control rats when perfused in vitro with the LH analog human chorionic gonadotropin (hCG). This decrease confirms that testicular responsiveness to LH, the hormone which regulates T secretion in vivo, is impaired by TCDD treatment. Because TCDD also reduced intratesticular T content, the decrease in T secretion is due to an inhibition of T synthesis rather than to a failure of the secretion process. These effects of TCDD are not secondary to undernutrition, because perfused testes from feed-restricted control rats were fully hCG responsive. TCDD treatment neither increased the hCG-stimulated secretion of any T precursor nor significantly decreased the efficiency with which testes converted the pregnenolone (PREG) they synthesized into T (PREG is the initial steroidogenic intermediate). In addition, TCDD did not inhibit T secretion when steroidogenesis was supported by exogenous PREG at approximately the in vivo rate. We conclude that TCDD does not inhibit the conversion of PREG to T. The inhibition of T biosynthesis must instead result from an inhibition of PREG formation. The finding that TCDD treatment substantially decreased the rate at which hCG-perfused testes secreted PREG and its metabolites (a decrease seen across all hCG concentrations) confirms this conclusion. This inhibition of LH/hCG-stimulated PREG formation by TCDD must be due to a reduction in the activity of the enzyme which converts cholesterol to PREG (cytochrome P450scc), and/or an impairment in the multistep process responsible for mobilizing cholesterol to this enzyme.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0041-008X
pubmed:author
pubmed:issnType
Print
pubmed:volume
106
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
112-25
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
1990
pubmed:articleTitle
Inhibition of testicular steroidogenesis in 2,3,7,8-tetrachlorodibenzo-p-dioxin-treated rats: evidence that the key lesion occurs prior to or during pregnenolone formation.
pubmed:affiliation
Environmental Toxicology Center, University of Wisconsin, Madison 53706.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.