Adrenergic control of red cell pH in salmonid fish: roles of the sodium/proton exchange, Jacobs–Stewart cycle and membrane

• Main Authors: Mikko Nikinmaa, Kirsti Tiihonen, Marita Paajaste
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1990
• Subjects: Carbonic acid
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.501.9470; http://jeb.biologists.org/content/154/1/257.full.pdf

We investigated the mechanisms by which adrenergic activation of sodium/pro-ton exchange reduces the pH gradient across the membrane of rainbow trout red cells. In untreated cells, adrenergic stimulation caused a significant increase in the proton distribution ratio ([H+]e/[H+]i) across the red cell membrane. The increase in the proton distribution ratio caused by adrenergic stimulation was inhibited by the protonophore 2,4-dinitrophenol (2,4-DNP). Thus, sodium/pro-ton exchange displaces protons from electrochemical equilibrium. Active regu-lation of intracellular pH by sodium/proton exchange is possible, because the extracellular dehydration of carbonic acid to carbon dioxide is uncatalyzed. The increase in proton distribution ratio caused by adrenergic stimulation was inhibited in red cell suspensions to which extracellular carbonic anhydrase had been added before stimulation. In contrast, inhibition of intracellular carbonic anhydrase markedly increased the pH changes induced by adrenergic stimulation, suggesting that the net direction of the intracellular hydration/dehydration reaction may markedly affect the intracellular pH changes. Membrane potential changes are not a necessary component of the adrenergic response. The increases in red cell volume and sodium and chloride concentrations induced by adrenergic stimulation were unaffected in cells 'voltage-clamped ' by valinomycin.