AJP - Regulatory, Integrative and Comparative Physiology, Vol 252, Issue 2 348-R352, Copyright © 1987 by American Physiological Society
Acid-base balance in ducks (Anas platyrhynchos) during involuntary submergence
M. Shimizu and D. R. Jones
Measurements of all the major independent variables [arterial CO2 tension
(PaCO2); strong-ion difference ([SID]), and total protein content, which
approximate total weak acid concentration in plasma] are essential for
understanding changes in acid-base balance in plasma. During involuntary
submergence of 1, 2, or 4 min, PaCO2 in ducks increased and arterial pH
(pHa) decreased. During 1-min dives there were no significant changes in
any strong ions. In both 2- and 4-min dives, there was a significant
increase in [lactate-], but because of an increase in equal magnitude of
[Na+], [SID] did not change. During recovery from all dives the plasma
remained acidotic for several minutes, although PaCO2 fell below predive
levels in less than 1 min. [Lactate-] increased in the recovery period.
There were no changes in total protein content during submergence or
recovery. Breathing 100% O2 before 2-min dives caused a reduction in
[lactate-] production and release during and after the dive, although due
to a marked increased in PaCO2, pHa fell as low as in 4-min dives after
breathing air. After 1 min of recovery, pHa returned to normal along with
the restoration of the predive level of PaCO2. We conclude that the
acidosis during involuntary submergence is due solely to an increase in
PaCO2, whereas in recovery it is caused by decreased [SID].
