[Sodium movement and distribution in the epithelial membranes].
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Epithelium↗
Biomedical subjects
M Cereijido
Publications and source records attributed to M Cereijido.
K fluxes in frog skin.
A method has been developed for measuring K influx into the epithelial cells of frog skin from the inside solution. Diffusion delay in the connective tissue has been taken into account. Ninety-four per cent of skin K was found to exchange with K(42) in the inside solution with a single time constant. K influx showed saturation with increasing K concentration, was not altered by imposing a potential difference of +/-200 mv across the skin, and was inhibited by dinitrophenol, fluoroacetate, and ouabain. Relatively low concentrations of dinitrophenol (5 x 10(-5)M) and fluoroacetate (10(-10)M) had no effect on k influx but caused a 40 per cent decrease in net Na flux. There was no correlation between the rate of K uptake at the "inner barrier" and the rate of net Na transport. Reduction of net Na transport by lowering Na concentration in the outside solution caused little change in K uptake. These observations indicate that there is not a significant Na-K exchange involved in active transport of Na across the skin. K influx was found, however, to require Na in the inside bathing solution.
Animals↗
[The role of cellular contacts in the recovery of the ion channels of epithelial cell membranes].
Cationic currents in mature MDCK cells are almost exclusively due to K+ channels. Harvesting with trypsin-EDTA destroys 80-90% of these channels. Upon replating, K+ currents recover in 12-20 h, by means a process that requires synthesis of proteins and of RNA. In the present work we demonstrate that this restoration depends on a Ca2+ activated-cell contact. Thus, cells in confluent monolayers bathed with 1.8 mM Ca2+ have a K+ current of 343 +/- 82 pA; confluent without Ca2+ have only 90 +/- 12 pA (27% of control; and without cell-cell contacts incubated with 1.8 mM Ca2+ (subconfl+Ca2+) have 104 +/- 21 pA (31% of control). This demonstration that the expression of K+ channels depends on Ca-activated cell-attaching molecules suggests that a molecule of the type of uvomorulin is involved.
Animals↗