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K+ and Cl transport by mammary secretory cell apical membrane vesicles isolated from milk

Published online by Cambridge University Press:  01 June 2009

David B. Shennan
Affiliation:
Hannah Research Institute, Ayr KA6 5HL, UK

Summary

The transport of K+ (Rb+) and Cl by membrane vesicles isolated from bovine milk has been studied using ion-exchange column chromatography. K+ (Rb+) and Cl accumulation by the vesicles was time-dependent and was almost abolished by 0·1% Triton X-100, suggesting that uptake represents ‘real’ transport rather than binding. K+ (Rb+) uptake was influenced by the anion in solution in a manner suggesting that influx is sensitive to changes in vesicle membrane potential. Similarly, Cl uptake was found to be sensitive to vesicle electrical potential: Cl influx was enhanced by inside positive potentials. Cl uptake was not saturable with respect to external Cl. The results suggest that K+ (Rb+) and Cl cross the apical membrane by way of conductance pathways. The similarity between ion transport by skim milk membrane vesicles and that of the apical aspect of the intact mammary epithelium suggests that the former may be a good model to study solute transport by the apical membrane of mammary secretory cells.

Type
Original Articles
Copyright
Copyright © Proprietors of Journal of Dairy Research 1992

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References

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