Ion transport by amphibian antrum in vitro. I. General characteristics

Both Necturus and bullfrog antrum show stable PD, resistance, and short-circuit current (Isc) when mounted in an Ussing chamber. Measurements of Na+ and Cl minus flux showed that both ions are actively transported across Necturus antrum, Na+ from secretory to nutrient, Cl minus from nutrient to secretory (both net fluxes being similar to 0.30 mueq cm minus 2 h minus 1). Only the Na+ transport contributed to the Isc and PD as evidenced by a) Na+ removal, b) the effects of amiloride on the secretory surface, c) the effects of ouabain on the nutrient side. Microelectrode experiments confirm the Na+ conductance of the secretory cell membrance, a HCO3 minus conductance of both cell membranes, and a KCl conductance across the nutrient cell membrane. In addition, antrum apparently secretes alkali (similar to 0.35 mueq cm minus 2 h minus 1), which secretion is sensitive to metabolic inhibitors and Diamox. Nutrientside HCO3 minus increased the rate of alkaline secretion and a transmucosal HCO3 minus gradient could contribute to ISC and PD. A model is proposed to account for the electrical properties of the tissue.