Key Points
- To compare myocardial force development, cellular energy state, and ATP production between hypoxia-tolerant freshwater turtles and hypoxia-sensitive rainbow trout during normoxia and severe hypoxia.
- Examined isolated ventricular preparations from freshwater turtles (at 20 °C) and rainbow trout (at 15 °C) under both resting conditions and electrically stimulated isometric twitch contraction at 30 min⁻¹.
- Measured twitch force, oxygen consumption, lactate production, cellular energy state, phosphorylation potential, and ATP hydrolysis rates across normoxic and severely hypoxic exposures.
- Both species underwent an approximately two-thirds metabolic depression in non-contractile processes during severe hypoxia, exhibiting similar rates of lactate production and residual oxygen consumption.
- Turtle ventricular preparations preserved higher cellular energy states and phosphorylation potentials while sustaining greater isometric twitch force throughout hypoxia relative to trout preparations.
- The ratio of twitch force development to total ATP hydrolysis increased markedly during hypoxia in turtle myocardium but remained unchanged in trout myocardium.
Structured PICO
PPopulationIsolated ventricular preparations from hypoxia-tolerant freshwater turtles (at 20 degrees C) and hypoxia-sensitive rainbow trout (at 15 degrees C)
IInterventionSevere hypoxia (preparations either at rest or stimulated at 30 min(-1) to develop isometric twitch force)
CComparatorNormoxia (oxygenated conditions)
OOutcomeForce development (isometric twitch force), cellular energy state, and ATP production (oxygen consumption and lactate production)surrogate
The superior economy of the contracting turtle myocardium during hypoxia, evidenced by a higher ratio of twitch force to ATP hydrolysis, may contribute to its remarkable hypoxia tolerance compared to trout.