On the mechanism of sodium-proton exchange in crayfish.
In salt depleted crayfish net sodium and proton fluxes were coupled 1:1 as required by the frog skin-turtle bladder model. In addition, three proton pump inhibitors produced equal reductions of both fluxes. It is concluded that the model operates in these animals. Net Na+ and H+ fluxes were very small in tap water adapted animals, but regression analysis clearly showed that they were coupled, though perhaps not 1:1. Proton pump inhibitors, at concentrations that suppressed fluxes in salt-depleted crayfish, had no measureable effect on proton movement in tap water-adapted animals. Two of them (dicyclocarbodiimide and N-ethyl maleimide), caused a small reduction in Na+ influx without affecting proton efflux. These experiments provide no support for operation of the frog-turtle system in adult crayfish adapted to tap water. A 2Na+-H+ exchanger is considered from an energetic point of view. Such a system might be able to couple Na+ and H+ fluxes in dilute, near neutral solutions ([Na+] approximately 1-2 mM; pH 7).
Zetino
A M
AM
School of Biological Sciences, Washington State University, Pullman, Washington, WA 99164-4236, USA.
Kirschner
L B
LB
Harvey
M
M
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003400:Astacoidea / Q000187:drug effects / Q000378:metabolism*; D001692:Biological Transport; D002712:Chlorides / Q000378:metabolism; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D007477:Ions / Q000378:metabolism; D018942:Macrolides; D054328:Proton Pump Inhibitors; D011522:Protons; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012492:Salts / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D002712:Chlorides; D004791:Enzyme Inhibitors; D007477:Ions; D018942:Macrolides; D054328:Proton Pump Inhibitors; D011522:Protons; D000644:Quaternary Ammonium Compounds; D012492:Salts; D004024:Dicyclohexylcarbodiimide; C036978:concanamycin A; D012964:Sodium; D005033:Ethylmaleimide