Kinetic analysis and partitioning of sodium and chloride influxes across the gills of sea water adapted trout.

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Abstract
Na and Cl influxes across the gills of sea water adapted trout were studied with the perfused isolated head technique. The hemodynamic scheme describing anastomoses between efferent gill arteries and the filamentous sinus was confirmed and utilized to determine partitioning of Na and Cl influxes. Two routes of Na and Cl entry were demonstrated, 1 lamellar and 1 sinusal. The lamellar Na and Cl fluxes were, respectively, 133 .+-. 21.8 and 271 .+-. 43.7 .mu.eq/h per 100 g. The sinus Na and Cl fluxes were: 50 .+-. 18.3 and 50 .+-. 11.3 .mu.eq/h per 100 g. The relative permeabilities of the apical and basal barriers of lamellar epithelium were determined with influx experiments coupled with radioactive unloading experiments. The basal membrane was 30 times less permeable than the apical to Na, while this ratio was 45 for Cl. The basal membrane represented the limiting factor in salt movement across the branchial epithelium. The intracellular pools of the lamellar compartment were calculated for Na: 1.1 .+-. 0.17 .mu.eq/100 g of fish wt; and for Cl: 5.1 .+-. 0.83 .mu.eq/100 g of fish wt.