Evidence for facilitated lactate uptake in lizard skeletal muscle

Area of Science:

• Comparative physiology
• Muscle metabolism
• Biochemistry

Background:

• Lactate metabolism is crucial for energy production in muscle.
• Understanding lactate transport in reptiles provides insights into evolutionary adaptations.
• Mammalian muscle lactate uptake is primarily mediated by monocarboxylate transporters.

Purpose of the Study:

• To investigate lactate uptake rates in lizard skeletal muscle.
• To compare reptilian lactate metabolism with mammalian systems.
• To determine the involvement of protein-mediated transport in lizard muscle lactate uptake.

Main Methods:

• Measuring lactate uptake rates in red (rIF) and white (wIF) iliofibularis muscles of lizards.
• Comparing uptake rates with mouse soleus muscle.
• Utilizing alpha-cyano-4-hydroxycinnamate to assess protein-mediated transport.
• Evaluating the effects of N-ethymaleimide on muscle energy status.

Main Results:

• Red iliofibularis (rIF) exhibited significantly higher lactate uptake rates than white iliofibularis (wIF) and mouse soleus.
• alpha-Cyano-4-hydroxycinnamate partially inhibited lactate uptake in rIF, indicating protein-mediated transport.
• N-ethymaleimide affected muscle energy levels, questioning its utility in reptilian studies.
• Higher lactate uptake in rIF correlates with its greater capacity for lactate utilization and glycogen synthesis.

Conclusions:

• Lactate uptake in reptilian muscle shares similarities with mammalian muscle.
• The monocarboxylate transport system for lactate appears to be evolutionarily conserved.
• Reptilian muscle lactate metabolism exhibits functional adaptations related to fiber type and energy demands.