Modes of Ammonia Transport Across the Gill Epithelium of the Marine Teleost Fish Opsanus Beta

摘要: The modes of ammonia transport across the gill epithelium marine teleost Opsanus beta were investigated using an isolated, perfused head preparation. During perfusion for approximately 2h there was no macro- or microscopic damage to exterior surface filaments lamellae, swelling structural leak only 0.3%, afferent pressure constant, and transepithelial electrical potential (TEP) approximated that measured in vivo . rate efflux similar , constant at least 80 min, approached zero when perfusate nominally ammonia-free. Addition ouabain bumetanide indicated basolateral Na+/NH4+ exchange, but not Na+/NH4+/2Cl− cotransport, important transbranchial transport. No evidence found apical exchange. Specific increases NH3 nearly 100 times as effective NH4+ concentrations stimulating efflux. Alteration TEPs could account any these effects. Calculated relative permeabilities indicate toadfish s relatively permeable compared shark other ‘tight’ epithelia, consistent with general conclusion gills are cation-‘leaky’. Computation roles three delimited pathways 22% is via 57% non-ionic diffusion 21% ionic NH4+. Comparison published data suggests epithelia may be correlated permeabilities.