Continuous monitoring of extracellular lactate concentration by microdialysis lactography for the study of rat muscle metabolism in vivo.
A method is described for the measurement and on-line monitoring of muscular extracellular lactate concentration in both anaesthetized and freely moving rats. This method is based on microdialysis sampling and lactic dehydrogenase-catalysed nicotinamide adenine dinucleotide, reduced (NADH)-fluorescence detection techniques. In vivo calibration revealed a resting extracellular lactate concentration of 1.92 +/- 0.13 mmol/l (+/- SEM) in the gastrocnemius muscle of adult male Wistar rats (n = 6), while the average whole-blood lactate level was 0.76 +/- 0.12 mmol/l (+/- SEM). This measured extracellular lactate concentration was 1.73-times higher than that deduced from the arterial lactate concentration. Blocking glycolysis with iodoacetate reduced the extracellular lactate concentration to 52 +/- 6% (+/- SEM, n = 4) of the resting level. The extracellular lactate concentration in rat gastrocnemius muscle had increased to significantly (P less than or equal to 0.05) different levels, 2.4 +/- 0.03 (+/- SEM) or 4.0 +/- 0.55 (+/- SEM) times the control value, 1 h after aortic clamping (n = 3) or cardiac arrest (n = 3), respectively. Stimulation of the sciatic nerve induced elevations of the extracellular lactate concentration in the tibialis anterior muscle which were linearly related to the recorded isometric force-time integral. We also monitored on-line the changes in extracellular lactate concentration in the tibialis anterior muscle of a swimming rat. Our results indicate that microdialysis lactate reflects also intracellular metabolism. Lactography may be a useful alternative to biopsies and nuclear magnetic resonance spectroscopy in clinical medicine and physiology for the monitoring of metabolism in vivo.
de Boer
J
J
Department of Biological Psychiatry, Academic Hospital Groningen, The Netherlands.
Postema
F
F
Plijter-Groendijk
H
H
Korf
J
J
D000818:Animals; D003956:Dialysis / Q000379:methods; D005110:Extracellular Space / Q000378:metabolism*; D006019:Glycolysis / Q000187:drug effects; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D007511:Ischemia / Q000378:metabolism; D007773:Lactates / Q000378:metabolism*; D019344:Lactic Acid; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods; D009132:Muscles / Q000098:blood supply / Q000378:metabolism*; D009994:Osmolar Concentration; D051381:Rats; D011919:Rats, Inbred Strains
D007461:Iodoacetates; D007773:Lactates; D019344:Lactic Acid; D019807:Iodoacetic Acid