Interpretation of current-voltage relationships for “active” ion transport systems: I. Steady-state reaction-kinetic analysis of class-I mechanisms

1981 ◽  
Vol 63 (3) ◽  
pp. 165-190 ◽  
Author(s):  
Ulf-Peter Hansen ◽  
Dietrich Gradmann ◽  
Dale Sanders ◽  
Clifford L. Slayman
Keyword(s):  
Steady State ◽  
Ion Transport ◽  
Kinetic Analysis ◽  
Reaction Kinetic ◽  
Class I ◽  
Transport Systems ◽  
Current Voltage ◽  
Active Ion Transport

Uptake of sodium and chloride by freshwater mussels

1979 ◽  
Vol 57 (1) ◽  
pp. 156-160 ◽  
Author(s):  
Thomas H. Dietz
Keyword(s):  
Steady State ◽  
North America ◽  
Ion Transport ◽  
Brackish Water ◽  
Major Ions ◽  
Chloride Transport ◽  
Freshwater Mussels ◽  
Transport Systems ◽  
Freshwater Bivalves ◽  
Chloride Influx

Ion transport rates were measured in six species representing the four families of freshwater bivalves in North America. Sodium and chloride transport systems function independently in all of the species. The unionid steady-state influx of Na and Cl was about 1 μ equiv/g dry tissue per hour. Margaritifera hembeli Na influx was about 5 μ equiv/g dry tissue per hour and they were in a positive Na balance. Chloride influx by M. hembeli was similar to the unionids. The Sphaeriacea transport Na and Cl at significantly higher rates than Unionacea. Corbicula manilensis Na and Cl influx was about 9 μ equiv/g dry tissue per hour. Sphaerium transversum Cl influx was similar to C. manilensis; however, Na influx was twice as high. The higher transport rates of the Sphaeriacea are similar to brackish-water animals. Sodium, Ca, and Cl are major ions in the blood of all species. Bicarbonate is a major anion (19–12 mM/L) in all species except C. manilensis (4 mM/L).

Passive and active ion transport by the urinary bladder of a euryhaline flounder

1984 ◽  
Vol 246 (4) ◽  
pp. F402-F408 ◽  
Author(s):  
J. R. Demarest ◽  
T. E. Machen
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Apical Cell ◽  
Apical Cell Membrane ◽  
Platichthys Stellatus ◽  
Current Voltage ◽  
Active Ion Transport ◽  
Voltage Clamping ◽  
Net Fluxes ◽  
Insight Into

The effects of voltage clamping on the flux ratios and unidirectional and net fluxes of Na and Cl were used to gain insight into the mechanisms of active and passive ion transport across urinary bladders isolated from seawater-(SW) and freshwater-acclimated (FW) flounder, Platichthys stellatus. Although the transepithelial conductance (Gt = 2.77 mS X cm-2) of FW bladders was much greater than that of SW bladders (Gt = 0.40 mS X cm-2), the current-voltage relationships of both SW and FW bladders were markedly nonlinear. Under short-circuit conditions there was a large difference in the serosal-to-mucosal Na flux (JNasm) between SW (0.10 mueq X cm-2 X h-1) and FW (1.71 mueq X cm-2 X h-1) bladders, but their mannitol permeabilities were identical. The results indicate that 1) the paracellular pathway of both SW and FW bladders is Cl selective and Cl movements through the shunt account for a maximum of 90% of Gt in SW bladders and 19% in FW bladders; 2) the larger Gt of FW bladders is due to greater conductance of the apical cell membrane; 3) the majority of the passive ion movement across these epithelia proceeds through nonconductive, presumably transcellular, pathways; and 4) active transport of Na and Cl occurs by neutral coupling to each other and to other unidentified ions.

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