Key Points
- Investigate how anoxia and acidosis depress cardiovascular performance in freshwater turtles and identify the physiological calcium mechanisms that preserve heart function.
- Assessed cardiovascular responses in intact freshwater turtles undergoing prolonged experimental submergence leading to anoxia and combined acidosis.
- Conducted in vitro tissue analyses using isolated turtle atrial and ventricular preparations exposed to varying extracellular calcium concentrations.
- Elevated extracellular calcium concentrations fully reversed the depressive actions of anoxia and acidosis on isolated atrial and ventricular contractility.
- Intact turtles responded to submergence-induced anoxia and acidosis by raising plasma calcium levels and releasing calcium from intracellular cardiac organelles to elevate sarcoplasmic calcium concentrations.
Structured PICO
PPopulationFreshwater turtles (in vivo and in vitro ventricular and atrial tissue)
IInterventionAnoxia and acidosis (experimental submergence) and increased extracellular Ca++ concentration
OOutcomeCardiac function and contractilitysurrogate
Turtles compensate for the cardiac depressant effects of anoxia and acidosis by increasing plasma and intracellular calcium levels to improve contractility.