A new approach to the assessment of anaerobic metabolism: measurement of lactate in saliva.

OBJECTIVE: To test the hypothesis that saliva lactate concentrations may reflect those present in blood and that saliva lactate can be used as a very convenient and useful variable in the study of anaerobic metabolism. METHODS: Parallel determinations were made of lactate in saliva and in capillary blood samples, obtained at 3 min intervals from nine individuals during the performance of a maximum graded exercise test on a cycle ergometer against increasing workloads (from 25 up to a maximum of 300 W). Lactate determinations were done by means of an electroenzymatic method using 25 microliters samples in both types of fluids. RESULTS: For each situation, the concentration of lactate in saliva was shown to be about 15% of that in plasma but it followed the same pattern of evolution during the exercise test. A good correlation (r = 0.81) between blood and saliva lactate concentrations was found. The precision of the method was very good, with a coefficient of variation ranging (n = 10) between 2.2% for samples with very low lactate concentrations and 0.7% for sample with moderate lactate concentrations. Lactate appeared to be very stable in saliva over a period of 40 days after collection, when kept at 4 degrees C. The values obtained after this period were virtually identical to those shown in fresh samples. CONCLUSIONS: Determination of lactate in saliva can be used as an alternative to determination in blood, overcoming most of the drawbacks of the procedures being used at present, since the collection of the samples required no special expertise.