Lactate uptake by skeletal bone in anoxic turtles, Trachemys scripta.

Area of Science:

• Comparative Physiology
• Biochemistry
• Herpetology

Background:

• Freshwater turtle shells are known to accumulate lactate during anoxic submergence.
• The role of other skeletal elements in lactate metabolism during anoxia remains largely unexplored.
• Understanding lactate buffering in reptiles is crucial for comprehending their survival strategies in low-oxygen environments.

Purpose of the Study:

• To investigate lactate uptake and concentration in various skeletal elements of the red-eared slider turtle (Trachemys scripta).
• To determine if the entire skeleton, similar to the shell, sequesters lactate during anoxic conditions.
• To assess the contribution of skeletal lactate sequestration to overall acid-base balance.

Main Methods:

• Measurement of lactate concentrations in 7 skeletal elements and 4 shell samples from control and anoxically submerged turtles (Trachemys scripta).
• Analysis of blood gas parameters (pH, PCO2, PO2) and plasma lactate levels in experimental animals.
• In vitro equilibration of bone samples with lactate solution to assess direct uptake and accumulation patterns.

Main Results:

• Anoxic submergence induced significant lactic acidosis, with plasma lactate reaching 45.6 ± 2.5 mmol/l.
• Lactate concentrations increased significantly in all tested shell and skeletal elements (30.1–43.9 mmol/kg) in anoxic turtles.
• Limb bones showed the highest lactate accumulation, while the skull exhibited the least, a pattern also observed in vitro.

Conclusions:

• The entire skeleton of the red-eared slider turtle, including limb bones and skull, sequesters lactate.
• Skeletal lactate sequestration plays a significant role in buffering lactic acid generated during prolonged anoxic submergence.
• This finding extends the known physiological adaptations of freshwater turtles to survive hypoxic environments.