1989 Fiscal Year Final Research Report Summary
Nutritional Regulation of Intestinal Bile Acid Reabsorption
| Project/Area Number |
63560092
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
応用生物化学・栄養化学
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| Research Institution | Kyoto Prefectural University |
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Principal Investigator |
IWAMI Kimikazu Kyoto Prefectural University, Department of Agricultural Chemistry, Associate Professor, 農学部, 助教授 (00026569)
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| Project Period (FY) |
1988 – 1989
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| Keywords | taurocholic acid / experimental diabetes mellitus / transport capacity for bile acids / dietary adaptation / circadian rhythm / affinity lebeling |
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| Research Abstract |
This investigation was designed to obtain some information on the nutritional regulation of intestinal bile acid reabsorption as a rink in the enterohepatic circulation. The experimental results are as follows:
(1) Rats that had been adapted to meal-feeding were given a definite amount of 20% soy protein- or casein-based diet containing 0.04 muCi of [^<14>C] taurocholate, and examined for intraluminal movement and mucosal accumulation of the radioactive bile acid. A significant difference was observed between both dietary groups in the amount of [^<14>C] aurocholate intraluminally left or taken up in the ileum. Namely the soy protein ingestion caused a reduction in the bile acid absorption across the intestinal wall, thereby raising its fecal excretion.
(2) The taurocholate uptake in rat small intestine was investigated with everted sacs and isolated epithelial cells. A Na^+-dependent bile acid transport was proved to be localized in the terminal ileum and to be negatively affected by fa
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sting over 2 days. This variation had reflected a diminution not in the affinity for bile acids but in the quantity of carrier protein.
(3) Meal-fed rats were examined for postprandial changes in Na^+-dependent bile acid transport capacities using isolated epithelial cells. This transport capacity didn't so much vary with postprandial time as the leucine uptake.
(4) Growing rats were allowed free access to diets with emphases of fat and carbohydrate, respectively, for 4 weeks or to mutually exchanged diets half-way during the feeding period. High-fat (low-carbohydrate) feeding led to a significant increase in the active bile acid transport rate per unit mucosal weight as compared with low-fat (high-carbohydrate) feeding. Similar tendencies were observed for the grounds with dietary exchange. The effect of diabetes mellitus on the ileal membrane transport system was also investigated, and the bile acid transport rate in alloxan-diabetic rat ileum was found to be not increased, or rather decreased, relative to that in normal rat ileum.
(5) Carrier proteins relating to a bile acid transport system were modified by affinity labeling with (7,7-azo-3alpha,12alpha-dihydroxy-5beta-cholan-24-olyl)-2-[^<14>C] aminomethanesulfonic acid, and then subjected to SDS-PAG electrophoresis. Protein bands with molecular sizes of 40K, 57K, 81K, 99K and 140K were radioactive, but reconstitution of active transport system with these components were unsuccessful in this experiment. Less
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