Electrolyte transport by gallbladders of rabbit and guinea pig: Effect of amphotericin B and evidence of rheogenic Na transport

Abstract

Ion transport and electrical properties of rabbit and guinea pig gallbladders were investigated to gain further information about the active transport mechanism that mediates fluid absorption. The intracellular and transepithelial electrical potentials were measured simultaneously using the microelectrode technique. Exposure of the mucosal surface to Amphotericin B resulted in the prompt development of a serosa-positive electrical potential difference (PD) which could not be attributed to an alteration in ion diffusion potentials across either the cell membrane or across the tight junction. Because the Amphotericin B-inducedPD was immediately dependent on warm temperatures and O₂, and was independent of NA and K concentration gradients across the cell membrane, it is suggested that active ion transport is directly responsible for thePD. Since thePD was abolished in the absence of Na in the bathing solutions, a rheogenic Na pump is postulated; this pump also appears to be operative in tissue not exposed to Amphotericin B. The specific tissue properties altered by Amphotericin B to produce a serosa-positivePD remain incompletely defined. The results of the present study indicate that ion transport by rabbit gallbladderin vitro is a consequence of a rheogenic active Na transport mechanism at the basolateral membranes which, in conjunction with a coupled NaCl influx process at the mucosal border, ultimately results in absorption of NaCl and water.