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Active NaCl absorption across posterior gills of hyperosmoregulating Chasmagnathus granulatus

Horst Onken^1,*, Martin Tresguerres² and Carlos M. Luquet²

¹ Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Avenida Bandeirantes 3900, Ribeirão Preto 14040-901, SP, Brasil
² Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pab. II, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina

View larger version (11K): [in a new window]   Fig. 1. Representative time course of measured Isc (Isc*) across split lamellae of posterior gills of C. granulatus, showing the effects of replacing Cl- (1, by nitrates) or Na+ (2, by choline) on both sides of the tissue. The vertical current deflections are due to 1 mV voltage pulses and reflect the uncorrected conductance across the preparation.

View larger version (10K): [in a new window]   Fig. 2. Representative time course of Isc* across split lamellae of posterior gills of C. granulatus, showing the influence of internal addition of 5 mmol l-1 ouabain (1). The vertical current deflections are due to 1 mV voltage pulses and reflect the uncorrected conductance across the preparation.

View larger version (12K): [in a new window]   Fig. 3. Representative time course of Isc* across split lamellae of posterior gills of C. granulatus, showing the effects of internal addition of 10 mmol l-1 BaCl2 (2) and 2 mmol l-1 diphenylamine-2-carboxylate (4, DPC as free acid). At (1) BaCl2 was added to the external bath as a control for diffusive movements of Ba2+ and Cl-. At (3) dimethylsulfoxide, the primary solvent for DPC, was added to the internal solution. The vertical current deflections are due to 1 mV voltage pulses and reflect the uncorrected conductance across the preparation.

View larger version (10K): [in a new window]   Fig. 4. Representative time course of Isc* across split lamellae of posterior gills of C. granulatus, showing the influence of external addition of 50 mmol l-1 CsCl (1). At (2) CsCl was also added to the internal bath as a control for diffusive movements of Cs+ and Cl-. The vertical current deflections are due to 1 mV voltage pulses and reflect the uncorrected conductance across the preparation.

View larger version (22K): [in a new window]   Fig. 5. Diagram showing the unidirectional influxes of Na+ across isolated posterior gills of C. granulatus in the absence (white column) and presence (grey column) of 0.1 mmol l-1 acetazolamide (AZ). Analysis of the two groups by paired Student's t-test revealed that the difference was significant at P=0.0007. See Materials and methods for details.

View larger version (18K): [in a new window]   Fig. 6. Proposed functional model for active NaCl absorption across the gill epithelium of hyperosmoregulating C. granulatus.