Heikki Savolainen, Dept. of Occup. Safety & Hlth., Tampere, Finland
13 August 2009
Dear Editor,
The excellent commentary summarizes the ideas how to approach the problem of hyperlactatemia (1). L-lactic acid is a physiological source of energy e.g. for brain which is why cell membranes have several isoforms of monocarboxylate transporters for its uptake(2).
It seems that in case of inadequate oxidative phosphorylation, excessive amounts of L-lactate is produced. Large L-lactate concentrations seem to inhibit its own uptake (3) thus increasing the extracellular pool.
A special case is the D-lactate, e.g. from hyperglycemia or propylene glycol containing drugs (4). While taken up by the transporters its metabolism is slow by the mitochondrial D-lactate oxidase leading to clinical acidosis as well.
1 Gutierrez G, Williams JD. The riddle of hyperlactatemia. Crit Care 2009; 13: 175.
2 Settle P, Mynett K, Speake P, et al. Polarized transport activity and expression in the syncytiotrophoblast of the term human placenta. Placenta 2004; 25: 496.
3 Majumdar S, Gunda S, Pai D, et al. Functional activity of monocarboxylate transporter, MCT1, in the human retinal pigmented epithelium cell line, ARPE-19. Mol Pharm 2005; 2: 109.
4 Talasniem JP, Pennanen S, Savolainen H, et al. Assay of D-lactate in diabetic plasma and urine. Clin Biochem 2008; 41: 1099.
Lactic acid transporters
13 August 2009
Dear Editor,
The excellent commentary summarizes the ideas how to approach the problem of hyperlactatemia (1). L-lactic acid is a physiological source of energy e.g. for brain which is why cell membranes have several isoforms of monocarboxylate transporters for its uptake(2).
It seems that in case of inadequate oxidative phosphorylation, excessive amounts of L-lactate is produced. Large L-lactate concentrations seem to inhibit its own uptake (3) thus increasing the extracellular pool.
A special case is the D-lactate, e.g. from hyperglycemia or propylene glycol containing drugs (4). While taken up by the transporters its metabolism is slow by the mitochondrial D-lactate oxidase leading to clinical acidosis as well.
1 Gutierrez G, Williams JD. The riddle of hyperlactatemia. Crit Care 2009; 13: 175.
2 Settle P, Mynett K, Speake P, et al. Polarized transport activity and expression in the syncytiotrophoblast of the term human placenta. Placenta 2004; 25: 496.
3 Majumdar S, Gunda S, Pai D, et al. Functional activity of monocarboxylate transporter, MCT1, in the human retinal pigmented epithelium cell line, ARPE-19. Mol Pharm 2005; 2: 109.
4 Talasniem JP, Pennanen S, Savolainen H, et al. Assay of D-lactate in diabetic plasma and urine. Clin Biochem 2008; 41: 1099.
Competing interests
None