1994 Fiscal Year Final Research Report Summary
Studies on physiological role of cellular retinolbinding protein, type II in small intestine
| Project/Area Number |
04670097
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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 |
環境生理学(含体力医学･栄養生理学)
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| Research Institution | University of Shizuoka |
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Principal Investigator |
TAKASE Sachiko University of Shizuoka, School of Food and Nutritional Sciences, Department of Nutrition, Professor, 食品栄養科学部・栄養学科, 教授 (10046196)
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| Co-Investigator(Kenkyū-buntansha) |
GODA Toshinao University of Shizuoka, School of Food and Nutritional Sciences, Department of N, 食品栄養科学部・栄養学科, 助手 (70195923)
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| Project Period (FY) |
1992 – 1994
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| Keywords | Cellular retinol-binding protein, type II / mRNA / vitamin A / beta-carotene / Fat / Retinoid X receptor / Intestinal villus |
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| Research Abstract |
1.The expression of intestinal CRBP (II) mRNA was detected in Day 18 chick embryo and its mRNA level rapidly increased around hatching.The developmental pattern of the CRBP (II) mRNA was in parallel with the pattern of CRBP (II) protein.Retinoid x receptor (RXR) mRNA was constantly expressed in embryonic and post-hatched chick intestines.
2.Synergistic effect of retinol and thyroid hormone on CRBP (II) induction occurred in organ culture of Day 16 chick embryonic duodenum.Its level remarkably increased in the medium added 9-cis retinoic acid.The addition of fatty acid (linoleate) or synthetic arachidonic acid analog (5,8,11,14-eicosatetraunoic acid) also increased CRBP (II) and its mRNA.
3.Feeding excess vitamin A,but not excess beta-carotene, caused accumulation of unesterified retinol which exceeded binding capacity of CRBP (II) in rat intestine.Rats fed excess vitamin A which was 1000 times the amount of the NRC's recommended requirement, showed the increase in lecithin : retinol acyltransferase (LRAT) activity.The CRBP (II) may play an important role in preventing toxic effect of unbound retinol in the small intestine, but there appears to be a limitation in retinol-binding capacity of CRBP (II) for over 10 times excessive retinol.
4.The jejunal CRBP (II) level in the aged rats (600 days-old) tended to be lower.
5.Distribution of CRBP (II) mRNA along villus-crypt axis of rat jejunum was somewhat different from that of CRBP (II) protein, showing that its gene level was low in differentiating lower villus and maximum in lower part of mid-villus.The villus-crypt gradient of jejunal LRAT activity was comparable to that of CRBP (II) protein, which showed a maximal level in the mid-villus and low levels in the apical villus and crypt.
The CRBP (II) mRNA and its protein levels in jejunum significantly elevated in rats fed a high fat (corn oil) diet.The expression of CRBP (II) gene is proposed to be modulated by long-chain unsaturated fatty acids or their metabolites.
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