The mechanisms of acid-base and ionoregulation in the freshwater rainbow trout during environmental hyperoxia and subsequent normoxia. II. The role of the kidney

Michele Wheatly, Helve Hobe, Chris M. Wood

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44 Scopus citations


Plasma ionic status and renal excretion of acidic equivalents and electrolytes were continuously monitored in the freshwater rainbow trout (Salmo gairdneri) during 24 h normoxia (PIO2 = 120-150 torr; control) 72 h hyperoxia (PIO2 = 500-600 torr), and 24 h return to normoxia. Plasma [Cl-] progressively declined in approximate equivalence to the rise in [HCO3 -] which compensated the respiratory acidosis of hyperoxia, while [Na+] increased only slightly. [Ca2+] and [K+] rose, [phosphate] declined, and [NH4 +] was unchanged. During normoxic recovery, the [Na+], [Cl-] and [HCO3 -] changes were reversed, [K+] and [Ca2+] showed further elevations, and [NH4 +] increased sharply. Renal acid output increased greatly during hyperoxia with elevations in both NH4 + and titratable components, though the latter predominated due to a marked elevation of phosphate excretion. Renal efflux rates of other electrolytes were generally homeostatic for ECF composition, with increased Na+, K+, and Ca2+ effluxes, and decreased Cl- efflux.Clearance calculations indicated that net tubular reabsorption increased for Cl-, fell for Na+ and K+, and changed over to marked net secretion for phosphate, while net ammonia secretion increased. Most tends were reversed upon return to normoxia. The critical role of phosphate in urinary electrolyte balance and acid-base regulation is emphasized. The net renal excretion of acidic equivalents accounted for only 7-10% of the total compensation observed for the whole animal during hyperoxia. The kidney contributed primarily in conserving ECF HCO3 - and secondarily in balancing branchial exchanges.

Original languageEnglish (US)
Pages (from-to)155-173
Number of pages19
JournalRespiration Physiology
Issue number2
StatePublished - 1984
Externally publishedYes



  • Acid-base balance
  • Hyperoxia
  • Phosphate
  • Plasma electrolytes
  • Renal function
  • Salmo gairdneri
  • Titratable acidity

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine

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