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Miyazaki-shi, Japan

Maeda Y.,Brestopia Hospital | Funagayama M.,Brestopia Hospital | Funagayama M.,University of Miyazaki | Shinohara A.,University of Miyazaki | And 6 more authors.
Hormone and Metabolic Research | Year: 2013

The aim of this study was to investigate the differences between rats and hamsters, Two of the most widely used experimental animals, with respect to the effects of microsomal membrane solubilization on the inhibition of liver 11β-hydroxysteroid dehydrogenase (11β-HSDI) enzyme by bile acids. Liver microsome fractions were prepared, and the 11β-HSDI enzymatic activity was measured using cortisone as a substrate. The substrate and various concentrations of bile acids were added to the assay mixtures. After incubation, the products were extracted and analyzed using high-performance liquid chromatography. To investigate the effect of detergent on the inhibitory effects of bile acids, we conducted inhibition tests using Triton X-100-solubilized animal liver microsomes. When solubilized microsomes were used, all bile acids inhibited 11β-HSDI from rats and hamsters to various degrees. 7α-Hydroxycholanoic acids (cholic acid and chenodeoxycholic acid) in particular had strong inhibitory activities. In hamsters, 7β- hydroxycholanoic acid (ursodeoxycholic acid) was the strongest inhibitor among the bile acids tested, although its effect was not very strong. When nonsolubilized microsomes were used, deoxycholic acid did not inhibit but rather enhanced the enzymatic activity in both animals. Microsomal content of cholesterol and phospholipids are significantly different between rats and hamsters. Species differences in bile acid inhibition of nonsolubilized microsomes might be reflected not only by structural difference of bile acids, which affect membrane solubilization and enzyme activity directly, but also species difference in microsomal membrane lipid content. © Georg Thieme Verlag KG Stuttgart, New York. Source


Maeda Y.,Brestopia Hospital | Funagayama M.,Brestopia Hospital | Shinohara A.,University of Miyazaki | Koshimoto C.,University of Miyazaki | And 6 more authors.
Journal of Physiology and Biochemistry | Year: 2014

The influence of human serum albumin (HSA) on the bile acid-mediated inhibition of liver microsomal type 1 11β-hydroxysteroid dehydrogenase (11β-HSD1) was studied in vitro. A rat liver microsomal fraction was prepared, and the 11β-HSD1 enzyme activity in the presence of various concentrations of bile acids and HSA was determined using hydrocortisone as the substrate. The products of the reaction were extracted and analyzed using high-performance liquid chromatography. The magnitude of the inhibition decreased with the addition of HSA in a dose-dependent manner. Four percent human albumin decreased the inhibitory effects of 100 μM chenodeoxycholic acid and lithocholic acid from 89.9 ± 5.6 to 54.5 ± 6.1 % and from 83.8 ± 4.8 to 20.8 ± 4.2 %, respectively. In contrast, ursodeoxycholic acid and deoxycholic acid showed no inhibitory effect on the enzyme activity in the presence of 4 % human serum albumin, and the addition of 1 % γ-globulin to the assay mixture in the presence of bile acids did not affect the enzyme activity. Our in vitro study showed that the addition of HSA ameliorated the inhibition of 11β-HSD1 and that the magnitude of the change is dependent on the species of bile acid, presumably based on the numbers of hydroxyl groups. These results suggest that HSA seems to protect the bile acid-mediated inhibition of 11β-HSD1 in the healthy subject. On the other hand, in the patients with obstructive biliary diseases, not only elevated serum bile acid but also the accompanying hypoalbuminemia is important to evaluate the pathophysiology of the bile acid-mediated inhibition of 11β-HSD1 of the disease. © 2014, University of Navarra. Source

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