title: Ventilatory regulation of extracellular pH in crayfish exposed to changes in water titration alkalinity and NaCl concentration.
abstract: The mechanisms of extracellular pH regulation were studied in normoxic crayfish Astacus leptodactylus during changes in water ionic composition at 13 degrees C. In artificial waters all ambient physico-chemical properties were controlled. Ventilatory changes and the time course of hemolymph acid-base balance, ABB, were followed after a decrease of water titration alkalinity, TAw, from 4 to 2 meq X L-1 simultaneously associated with either an increase of NaCl concentration, [NaCl]w, from 0.5 to 5 mmol X L-1, or a decrease of [NaCl]w, from 0.5 to 0.15 mmol X L-1. The ABB changes were characterized by a hypercapnic acidosis attributable to the decrease of TAw. Depending on the simultaneous change of [NaCl]w, two different mechanisms of compensation were observed. When [NaCl]w increased, the compensation was metabolic: the ventilatory requirement, VW X MO2-1, did not vary. When [NaCl]w decreased, the compensation was ventilatory: VW X MO2-1 doubled. It is concluded that in water-breathers ventilation, contrary to what is generally accepted, can play a role in extracellular ABB regulation.
mesh_terms: D000136:Acid-Base Equilibrium; D000818:Animals; D003400:Astacoidea / Q000502:physiology*; D006458:Hemolymph / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D008297:Male; D012119:Respiration; D012965:Sodium Chloride / Q000378:metabolism*
chemical_list: D012965:Sodium Chloride