title: Effect of ACTH suppression on adrenal 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA in 4-aminopyrazolopyrimidine-treated rats.
abstract: 4-Aminopyrazolopyrimidine (4-APP) treatments to rats for 3 days induced 2-fold increase of circulating ACTH and 11-fold increase of adrenal 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase mRNA compared to NaCl-treated controls. This in vivo model was used to study the effect of the suppression of ACTH secretion on the adrenal HMG-CoA reductase mRNA level. Dexamethasone (Dex) administration to 4-APP-treated rats caused a rapid and parallel decline of the levels of plasma ACTH and adrenal HMG-CoA reductase mRNA to 50% within 2.5 h, whereas the free and esterified cholesterol content was increased 5 and 9.4 times respectively. These changes could be counteracted by the co-administration of ACTH with Dex. Aminoglutethimide (AG) administration to 4-APP-treated rats, which increased the adrenal esterified cholesterol content (7.5 times), decreased the HMG-CoA reductase mRNA level (44%), despite plasma ACTH level remaining elevated. Moreover, the participation of newly synthesized protein(s) in the lowering of adrenal HMG-CoA reductase mRNA level induced by ACTH suppression is suggested by the fact that cycloheximide (Cyclo), when co-administered with AG, completely blocked the decrease of HMG-CoA reductase mRNA level, despite the plasma ACTH level decreasing by 68% and the free and esterified cholesterol content increasing 3.9 and 12.3 times, compared to 4-APP-treated rats. Furthermore, the specificity of these effects was established by the fact that the beta-actin mRNA level was not affected by the administration of either Dex, AG, Cyclo, or AG + Cyclo to 4-APP-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Faculty of Medicine, University of Sherbrooke, Canada.
authors.forename: J G
authors.initials: JG
authors.lastname: Lehoux
authors.forename: A
authors.initials: A
authors.lastname: Lefebvre
authors.forename: S
authors.initials: S
authors.lastname: Bélisle
authors.forename: D
authors.initials: D
authors.lastname: Bellabarba
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000311:Adrenal Glands / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000616:Aminoglutethimide / Q000494:pharmacology; D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D015152:Blotting, Northern; D002784:Cholesterol / Q000097:blood; D003513:Cycloheximide / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D006903:Hydroxymethylglutaryl CoA Reductases / Q000235:genetics*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D013997:Time Factors
chemical_list: D000924:Anticholesteremic Agents; D012333:RNA, Messenger; D000616:Aminoglutethimide; C004420:4-aminopyrazolo(3,4-d)pyrimidine; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D002784:Cholesterol; D003513:Cycloheximide; D006903:Hydroxymethylglutaryl CoA Reductases; D000225:Adenine