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Abstract

Effect of chenodeoxycholic acid on 11β-hydroxysteroid dehydrogenase in various target tissues (HTML) 
Morris,David J.; Souness,Graham W.; Latif,Syed A.; Hardy,Matthew P.; Brem,Andrew S.
Metabolism 53(6): 811-816
Publication date: 2004

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Glucocorticoids are metabolized by isoforms of the enzyme 11ß-hydroxysteroid dehydrogenase (11ß-HSD). There is some controversy concerning the bile acid, chenodeoxycholic acid (CDCA), as a potential endogenously produced inhibitor of 11ß-HSD. The present experiments were designed to determine the relative specificity of CDCA for both isoforms of 11ß-HSD and to assess the biological relevance of inhibition in vascular tissue. IC50 values (concentrations which inhibit 50% of the enzyme reaction) were calculated using rat liver microsomes as a source of 11ß-HSD1 dehydrogenase, Leydig cells for 11ß-HSD1 dehydrogenase and reductase, aorta for 11ß-HSD1 dehydrogenase and reductase, and sheep kidney for 11ß-HSD2 dehydrogenase. In each case, CDCA functioned as a potent inhibitor of 11ß-HSD1 dehydrogenase with IC50 values of ranging from 0.2 to 7 µmol/L in contrast to 37 to 200 µmol/L for 11ß-HSD1 reductase. CDCA exhibited relatively weak inhibitory activity against 11ß-HSD2 from sheep kidney with an IC50 of 70 µmol/L. The effect of CDCA on vascular contraction was studied in aortic rings isolated from Spague-Dawley rats incubated in medium containing corticosterone 10 nmol/L ± CDCA (1 µmol/L) for 24 hours. Rings were stimulated with graded concentrations of phenylephrine (PE) (10 nmol/L, 100 nmol/L, and 1 µmol/L). Rings exposed to corticosterone and CDCA consistently demonstrated a greater contractile response at lower doses of PE (63% at PE 10 nmol/L, P < .001; 20% at PE 100 nmol/L, P < .025; and 10% at PE 1 µmol/L, not significant [NS]) compared to control preparations incubated with cortiosterone alone. These studies demonstrate (1) that CDCA preferentially affects 11ß-HSD1 dehydrogenase; (2) CDCA does inhibit 11ß-HSD2 dehydrogenase and 11ß-HSD1 reductase but only at high(er) concentrations exceeding 70 µmol/L and 37 µmol/L, respectively; and (3) inhibition of 11ß-HSD1 dehydrogenase in aortic rings by CDCA (1 µmol/L) enhances the contractile response of corticosterone plus PE.

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