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Regional blood-brain lactate influx
J C LaManna1, J F Harrington, L M Vendel
1Department of Neurology, University Hospitals of Cleveland, OH.
Brain Research
|June 18, 1993
Summary
Brain lactate transport involves both saturable and diffusion mechanisms. At normal levels, these pathways contribute equally to lactate influx, with diffusion increasing at higher concentrations.
Area of Science:
- Neuroscience
- Physiology
- Biochemistry
Background:
- Lactate is a crucial energy substrate for the brain.
- Understanding blood-brain barrier transport is vital for neurological function and disease research.
Purpose of the Study:
- To quantify regional blood-to-brain lactate transport in rats.
- To differentiate between saturable and diffusional transport mechanisms.
- To determine the kinetic parameters of lactate influx.
Main Methods:
- Utilized a single-pass, dual-label indicator fractionation technique in anesthetized rats.
- Injected radiolabeled lactate analogs via the right atrium to measure brain uptake.
- Differentiated transport components based on stereospecificity and saturation kinetics.
Main Results:
- Identified both saturable, stereospecific (L-lactate) and non-saturable, non-stereospecific (diffusion) lactate influx components.
- Saturable transport exhibited low efficiency and moderate capacity (Km: 6-14 mM, Vmax: 23-40 µmol/100 g/min).
- Probenecid did not inhibit lactate transport; diffusion coefficients ranged from 0.020-0.036 ml/g/min.
Conclusions:
- Blood-to-brain lactate transport is mediated by distinct saturable and diffusional pathways.
- At physiological plasma lactate levels (1-1.5 mM), both components contribute equally.
- The contribution of diffusion increases with elevated plasma lactate concentrations.