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| Content Provider | PubMed Central |
|---|---|
| Author | Fan, C. C. Powell, D. W. |
| Abstract | The role of Ca2+ and calmodulin in regulating coupled NaCl transport has been investigated in membrane vesicles from rabbit ileal brush border. Uptake of 22Na+ and 36Cl- was determined by a rapid filtration technique in vesicles isolated with a sucrose density gradient ultracentrifugation method. Ca2+ on the inside of the vesicle inhibited Na+ uptake when Cl- was the anion and Cl- uptake when Na+ was the cation by approximately equal to 30%. Ca2+ on the outside had no effect. When gluconate was the anion or when choline was the cation, Na+ or Cl- uptake was reduced by only 9-12%. A similar inhibition of D-[3H]mannitol uptake (10-17%) suggests this was due to a nonspecific decrease in the membrane permeability. Other cations such as Ba2+ and Mg2+ had no effect, but La3+ inhibited Na+ and Cl- uptake to the same degree as Ca2+. Calmodulin (2 microM) in combination with Ca2+ (1 microM, free concentration) significantly inhibited Na+ uptake when Cl- was the anion by 21-32% and Cl- uptake when Na+ was the cation by 20-27%. This effect was completely reversed by 10 microM trifluoperazine. When gluconate was the anion or when choline was the cation, Na+ or Cl- uptake was unaffected by Ca2+/calmodulin and trifluoperazine. The Ki for Ca2+ inhibition of Cl- -coupled Na+ uptake was reduced from 200 microM to 0.2 microM by incubation with 20 microM calmodulin. The Ki for exogenously added calmodulin studied at 1 microM Ca2+ was 0.2 microM. The Ki for trifluoperazine inhibition of the Ca2+/calmodulin response was 3 microM. These results represent compelling evidence for intracellular Ca2+/calmodulin regulation of coupled NaCl transport across the intestinal microvillus membrane. The exact mechanism of this regulation remains to be delineated. |
| Starting Page | 5248 |
| File Format | |
| ISSN | 10916490 |
| e-ISSN | 10916490 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Issue Number | 17 |
| Volume Number | 80 |
| Language | English |
| Publisher Date | 1983-09-01 |
| Access Restriction | Open |
| Subject Keyword | Research in Higher Education |
| Content Type | Text |
| Resource Type | Article |
| Subject | Multidisciplinary |
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