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

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-induced PD 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 the PD. Since the PD 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 tissues not exposed to Amphotericin B. The specific tissue properties altered by Amphotericin B to produce a serosa-positive PD remain incompletely defined. The results of the present study indicate that ion transport by rabbit gallbladder in vitro is a consequence of a rheogenic active Na transport mechanism at the basolateral membranes which, in conjunction with a coupled NaC1 influx process at the mucosal border, ultimately results in absorption of NaC1 and water.