Correlation between damping coefficients and externally injected currents in oscillations produced by lithium ions in frog skin.

Oscillations in the electrical parameters elicited by Li+ added to the mucosal side of frog skin in vitro were studied under different experimental conditions. The correlation between the damping coefficient and the size of the externally injected current was ascertained. The size of the overall epithelial resistance in NaCl-Ringer seems to be a good indicator of the qualitative behaviour of the skin in the presence of Li+: the higher the resistance the less probable the occurrence of oscillations. Addition of amiloride allowed the calculation of the electromotive force in Na+- and Li+-Ringer. Calculations of the 'total equivalent inductance' and 'total equivalent capacitance' of an oscillating skin were made using resistance values (R), damping coefficients (sigma) and frequency of oscillation (omega).

Short circuit current and total conductance measurements on rat ileum.

1. Short circuit current and total conductance measurements were made on preparations of rat terminal ileum, using either the intact tissue or the isolated epithelium.2. The effects of D-glucose, 3-O-methyl-D-glucose, and 3-deoxy-3-fluor-D-glucose, added in suitable concentrations to the external bathing medium, were studied.3. An increase in both short circuit current and total conductance was detected when these sugars were used. It was possible to determine a linear relationship between the two variables and to study the kinetics of the interaction of glucose and 3-O-methyl-D-glucose with the sodium sugar carrier by using increasing concentrations of these substances.4. The increases in short circuit current and total conductance were also verified in isolated epithelium.5. Phlorizin, or the withdrawal of glucose, reversed the increase in short circuit current, but the total conductance remained unchanged.6. Increasing concentrations of 2-deoxy-D-glucose added to the mucosal bathing medium caused a decrease in short circuit current without changing the total conductance, either in preparations of intact ileum or in isolated epithelium.7. The meaning of these variations in the electrical parameters of the preparations is discussed.