1997 Fiscal Year Final Research Report Summary
Expression of Na channel after total colectomy in remnant ileal epithelium.
| Project/Area Number |
07457266
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Digestive surgery
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| Research Institution | Tohoku University |
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Principal Investigator |
SASAKI Iwao Tohoku University, Dept.of Medicine, Associate professor, 医学部, 助教授 (60125557)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Yuichi University od Shizuoka, Scool of Food and Nutritional Sciences, Laboratory of Ph, 食品栄養科学部, 教授 (50091707)
FUNAYAMA Yuji Tohoku University, Dept.of Medicine, Lecturer, 医学部, 講師 (50192315)
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| Project Period (FY) |
1995 – 1997
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| Keywords | total colectomy / electrophysiology / molecular biology / Na channel / aldosterone / epithelial cell |
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| Research Abstract |
Background & Aims : It has been known that in patients with proctocolectomy, epithelial transport functions in the remnant small intestine can be regulated in response to the increased fecal electrolyte and fluid loss. By using rat colectomy model, we investigated the Na and K transport mechanisms underlying the intestinal response. Methods : Proctolectomy with ileo-anal anastomosis was performed on Spregue-Dawley rats. Short-circuit current and 22Na fluxes were measured in isolated intestinal segment. Expression of mRNA for epithelial Na channels in the intestine was determined by Northern-blot analysis. Results : Amiloride (100micromol/L,mocosal side) and an amiloride analog benzamil (10micromol/L,mocosal side) reduced short-circuit current and 22Na absorption in the terminal ileum in proctocolectomized rats, but not in control rats. The activities of amirolide-sensitive short-circuit current expanded to a more proximal part (still within the ileum) between 2 and 4 wk after proctocolectomy. Plasma level of aldosterone was markedly elevated and the elevated fecal Na concentration was remarkably reduced during this period. Expression of mRNA for alpha-, beta-and gamma-subunit of epithelial Na channels in the lower small intestine was low in control, but was remarkably elevated in proctocolectomized rats. The short-circuit current, which is inhibited by tetraehyl anmonium (2 mmol/L,mucosal side), was also activated in the ileum of the colectomized rats specially in close association with the amiloride-sensitive short-circuit current. Conclusions : The electrogenic Na absorption and probably also tetraethyl ammonium-sensitive electrogenic K secretions are induced in the lower small intestine after proctocolectomy. These induction is caused by the increase of all three types of subunits, alpha-, beta- andgamma-rENaC mRNA at the transcription level. These processes may contribute to the recovery from the increased fecal Na loss.
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