The effect of amiloride on the transepithelial potential difference of the distal tubule of the rat kidney.

Microelectrodes with relatively large tips (3-5 mu O.D.) were used to measure the transepithelial potential difference (PD) of the distal tubule of the rat kidney in the control state and following i.v. administration of amiloride. This drug produced an increase in the magnitude of the positive PD in early distal segments (from +8.0 to +10.5 mV) and a change in polarity of the PD in late distal segments (from -18.0 to +2.5 mV). These data suggest that the potassium-conserving properties of the drug are due to its ability to induce an unfavorable electrochemical gradient opposing passive potassium secretion along the distal tubule.