Identification of a V-type proton pump in the outer mantle epithelium of Anodonta cygnea |
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Authors: | A. Rebelo da Costa P. F. Oliveira C. Barrias H. G. Ferreira |
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Affiliation: | a Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua de Campo Alegre 823, 4150 Porto, Portugal;b Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Porto, Portugal;c Departamento de Química, Universidade Nova de Lisboa, Lisboa, Portugal |
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Abstract: | The dissected outer mantle epithelium (OME) of Anodonta cygnea, when mounted in Ussing type chambers, generated a spontaneous potential difference of 22.0±12.6 mV and, when short-circuited, a positive current (Isc) of 30.0±11 μA/cm2 towards the shell side and a conductance of 1.1±0.4 mS/cm2. When in contact with the shell side, Bafilomycin A1 and Concanamycin A, specific inhibitors of V-proton pumps, induced 90% inhibition of Isc in 5 and 35 min, respectively. They had no effect in the current from the hemolymph side. Both drugs induced a dramatic fall in conductance from the shell side. Tributyltin oxide (TBTO) inhibited 90% of the Isc in 3 min and induced a fall in conductance only from the shell side. Two observations suggest a direct effect on the proton pump: it was effective only from the shell side and the time course of the effect was identical to that of Bafilomicyn A1. Dicyclohexycarbodiimide (DCCD) and N-ethylmaleimide (NEM) inhibited Isc from both sides but very slowly and there was a delay of the effect from the hemolymph side in relation to the shell side. Taken together, the results suggest the presence of a V-type proton pump located at the apical (shell side) barrier of the OME. |
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Keywords: | Anodonta Inhibitors Outer mantle epithelium V-type proton pump Bafilomicin A1 Concanamycin A TBTO |
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