Increasing magnitude of electrical potential along the renal distal tubule.

~~IGI-IT, FRED s. Increasing magnitude of electrical potential along the renal distal tubule. Am. J. Physiol. 220(3): 624-638. 1971.The magnitude of the transepithelial electrical potential (PD) was examined along the length of the distal tubule of rats. To determine whether the PD is constant along the length of the tubule, several methods were used to identify distance from the beginning of the distal convolution and to confirm the location of the tip of the microelectrode. In the first third of the distal tubule the PD averages 9-l 2 mv, lumen negative. In the last half of the tubule the PD exceeds -45 mv as previously reported by others. Additional experiments were done to assess the passive permeability properties of early and late distal segments. The tubule lumen was perfused with solutions of varying Na and K concentrations while the PD and wall resistance were measured. Relative conductances for Na and K were not different in early and late portions of the tubule. The transepithelial PD increases along the length of the distal tubule. Diffusion potentials alone do not account for the observed PD.