Blood acid-base regulation during environmental hyperoxia in the rainbow trout (Salmo gairdneri)

摘要: Blood acid-base balance, blood gases, respiration, ventilation, and renal function were studied in the rainbow trout during following sustained environmental hyperoxia (PIO2 = 3.50-650 Torr). Animals chronically fitted with dorsal aortic cannulae for repetitive sampling, oral membranes measurement of bladder catheters continuous urine collection. Hyperoxia caused a proportional increase arterial O2 tension stable 60% reduction ventilation volume (Vw), latter mainly due to decrease ventilatory stroke volume. consumption exhibited short-term elevation. Arterial CO2 (PaCO2) rose within 1 h, causing an immediate drop pH (pHa), continued gradually thereafter, reaching value 2-4x normoxic control level after 96-192 h. Compensation associated acidosis by accumulation [HCO3-] plasma started 5-6 was complete 48 Therefore, further compensation occurred simultaneously gradual rise PaCO2. The kidney played important active role this preventing excretion accumulated [HCO3-]. Upon reinstitution normoxia, PaCO2 dropped levels restoration status had commenced time. A return values 20 During hyperoxia, experimental elevation depressed Vw above only minor transient no change pHa, but injection branchial vasodilator 1-isoprenaline (10 mumol/kg) produced large pHa. It is concluded that internal diffusive and/or perfusive limitation vasoconstriction, rather than external convective decreased Vw.