Sodium-dependent copper uptake across epithelia: a review of rationale with experimental evidence from gill and intestine

摘要: The paper reviews the evidence for apparent sodium-dependent copper (Cu) uptake across epithelia such as frog skin, fish gills and vertebrate intestine. Potential interactions between Na(+) Cu during transfer through epithelial cells is rationalized into major steps of solute transfer: (i) adsorption on to apical/mucosal membrane, (ii) import in cell (iii) intracellular trafficking, (iv) export from blood. Interactions transport are most likely (ii). These ions have similar mobilities (lambda) solution (lambda, Na(+), 50.1; Cu(2+), 53.6 cm(2) Int. ohms(-1) equiv(-1)); consequently, Cu(2+) may compete equally with diffusion membrane surfaces. We present new data binding characteristics gill surface (gill microenvironment) rainbow trout. external trout saturation ligands at nanomolar concentrations solutes. At mucosal/apical several (fish gills, intestine), there both a Cu-specific channel (CTR1 homologues) leak channels (ENaC). slows amiloride-sensitive short circuit current (I(sc)) suggesting amiloride-binding site ENaC. examples isolated perfused catfish intestine showing that whole was reduced by 50% presence 2 mM luminal amiloride, 75% overall inhibition attributed an region middle Removal produced more variable results, but also together support modulation ENaC, not competitive entry However, situations where only few millimoles frogs freshwater), ENaC possible. CTR1 route when higher (e.g. intestinal epithelia). trafficking or unlikely. effects chloride Cu-ATPase indicate might indirectly alter flux. Conversely, inhibit basolateral Na(+)K(+)-ATPase increase [Na(+)](i).