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  • Title: Effect of ACTH suppression on adrenal 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA in 4-aminopyrazolopyrimidine-treated rats.
    Author: Lehoux JG, Lefebvre A, Bélisle S, Bellabarba D.
    Journal: Mol Cell Endocrinol; 1990 Feb 12; 69(1):41-9. PubMed ID: 2157616.
    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)
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