Oxidation of Lactate in Rats After Short-Term Strenuous Exercise

Abstract

Oxidation of lactate and glucose was investigated in rats after short-term strenuous running to exhaustion at a speed of 80 ∼ 110 m·min^-1, lasting about 100 sec. Immediately after the exercise, 4 µCi of [U-¹⁴C]lactate (LA and AR) or 9.4 µCi of [U-¹⁴C]glucose (GL) was injected into the aorta through an indwelling catheter. In AR, the rats ran at a speed of 25 m·min^-1 for 20 min after injection of [U-¹⁴C]lactate. Expired gas was collected by a bottomless metabolism chamber while the rats were on the treadmill for 120 min. Blood lactate concentration tended to decrease faster in AR than in LA. Peak evolution of ¹⁴CO₂ expiration occurred at 12.5 min recovery in LA, 7.5 min of recovery in AR, and 35 min of recovery in GL. Cumulative percent recovery of ¹⁴C as ¹⁴C0₂ was 48.5%±2.8% in LA, 74.0%±2.9% in AR, and 18.6%±1.6% (mean±SE) in GL. Significant differences were found in these rates between groups (P < 0.01). It was suggested that a great deal of lactate was oxidized directly, not after conversion to glucose in rats after short-term strenuous exercise to exhaustion and mild exercise following strenuous exercise (active recovery) enhanced lactate oxidation.

Key words

rats - exercise - recovery - lactate - glucose - oxidation