Rates of ion movement from plasma to endolymph in the dogfish.
The rates of movement of Na+, Rb+, Cl- and HCO3- from plasma to endolymph were studied in the elasmobranch fish, Squalus acanthias, by use of the appropriate isotopes. Rb+ was used as a marker for K+. The half-times to equilibrium for Na+, Rb+ and Cl- were about 100 hours; for HCO3- it was 6 hours. The equilibrium ratios, endolymph/plasma, are Na+ 0.87, K+ 26, Cl- 1.37, HCO3- 1.47. Carbonic anhydrase inhibition decreased the rate of HCO3- accumulation, suggesting that the process is actually the formation of endolymphatic HCO3- from plasma or tissue CO2. Increase in plasma pCO2 elevates endolymph HCO3- concentration. The secretory tissue contains carbonic anhydrase and Na-K-ATPase. These and other data suggest that a dominant feature of endolymph chemistry may be HCO3- formation linked in some fashion with K+ transport, through rates catalyzed by these two enzymes.
D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood / Q000494:pharmacology; D002256:Carbonic Anhydrases / Q000378:metabolism; D004284:Dogfish / Q000033:anatomy & histology / Q000097:blood / Q000378:metabolism*; D007758:Ear, Inner / Q000033:anatomy & histology / Q000201:enzymology; D004573:Electrolytes / Q000097:blood / Q000378:metabolism*; D004710:Endolymph / Q000187:drug effects / Q000378:metabolism*; D004976:Ethacrynic Acid / Q000494:pharmacology; D007700:Kinetics; D007761:Labyrinthine Fluids / Q000378:metabolism*; D010498:Perilymph / Q000378:metabolism; D012754:Sharks / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D004573:Electrolytes; D002245:Carbon Dioxide; D002256:Carbonic Anhydrases; D000254:Sodium-Potassium-Exchanging ATPase; D004976:Ethacrynic Acid; D000086:Acetazolamide