Anaerobic metabolism, gas exchange, and acid-base balance during hypoxic exposure in the channel catfish,Ictalurus punctatus
✍ Scribed by Burggren, Warren W. ;Cameron, James N.
- Publisher
- John Wiley and Sons
- Year
- 1980
- Tongue
- English
- Weight
- 942 KB
- Volume
- 213
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
Gill ventilation, blood gas and acid-base values, Mo,, Mc.02 and the gas exchange ratio have been measured before, during, and after exposure to hypoxia in the channel catfish, Zctalurus punctatus.
Z.punctatus maintains M,,, at control levels to a PI,, as low as 60 mm Hg, through a profound branchial hyperventilation. Concomitantly, however, a lactic acidosis usually develops, indicating a significant anaerobic glycolysis. Both a metabolic acidosis and respiratory alkalosis occur inzctalurus during hypoxic exposure, with the former usually predominating. MCo, doubles and the gas exchange ratio (R,) increases from 0.8 at control levels to 2.0 a t hypoxic levels, indicating that, in addition to anaerobic glycolysis, nonglycolytic pathways producing CO, also operate during hypoxic exposure. Analysis reveals that a t least half of the increased MCo2 during hypoxic exposure is due strictly to lactate acidification of the tissue HCO,pool, rather than from metabolic production of molecular CO,. Thus, the actual respiratory quotient (RQ) only rises to 1.5 during hypoxic exposure.
Within one hour of a return to air saturated water, a large lactate "flush" and severe plasma acidosis occur, and control levels for these and other values are not reachieved for 2-6 hours after hypoxic exposure.
Complete analysis of 0, and CO, exchange in the catfish exposed to short-term hypoxia thus must consider both the time course of acid-base disturbance and the evolution of CO, from the acidified tissue bicarbonate pool.