Relationship of the Donnan potential to the transmembrane pH gradient in tracheal apical membrane vesicles |
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Authors: | Jane E Langridge-Smith William P Dubinsky |
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Institution: | (1) Department of Physiology and Cell Biology, University of Texas Health Science Center at Houston, 77025, Texas;(2) Present address: Department of Zoology, University of Edinburgh, Edinburgh, Scotland |
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Abstract: | Summary Experiments were performed to determine the factors which contribute to the transmembrane pH gradient ( pH) and the potential gradient (![Delta](/content/w9855176713x5170/xxlarge916.gif) ) in apical plasma membrane vesicles isolated from bovine tracheal epithelium. As indicated by the accumulation of14C-methylamine, the vesicles maintained a pH (inside acidic) which was dependent upon the external pH. The pH was also proportional to the ionic strength of the suspending medium, suggesting that the H+ distribution was dictated by a Donnan potential. Measurements of the distribution of86Rb+ demonstrated an electrical potential gradient across the vesicle membrane, inside negative which was proportional to the medium ionic strength. pH changed in parallel with ![Delta](/content/w9855176713x5170/xxlarge916.gif) in response to a variety of imposed conditions. These results are compatible with the existence of a H+ conductance in the vesicle membrane. Thus the endogenous electrical and proton gradients may be manipulated and used as a general experimental tool to complement kinetic analysis in investigations of transport mechanism using isolated vesicle preparations. |
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Keywords: | membrane potential pH gradient membrane vesicles trachea |
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