Chronic elevated lactate levels are associated with insulin resistance in patients with type 2 diabetes mellitus (T2DM). Furthermore, lactacidosis plays a role in limiting physical performance. Erythrocytes, which take up lactate via monocarboxylate transporter (MCT) proteins, may help transport lactate within the blood from lactate-producing to lactate-consuming organs. This study investigates whether cycling endurance training (3 times/week for 3 months) alters the basal erythrocyte content of MCT-1, and whether it affects lactate distribution kinetics in the blood of T2DM men (n = 10, years = 61 ± 9, body mass index = 31 ± 3 kg/m(2)) following maximal exercise (WHO step-incremental cycle ergometer test). Immunohistochemical staining indicated that basal erythrocyte contents of MCT-1 protein were up-regulated (+90%, P = 0.011) post-training. Erythrocyte and plasma lactate increased from before acute exercise (= resting values) to physical exhaustion pre- as well as post-training (pre-training: +309%, P = 0.004; +360%, P < 0.001; post-training: +318%, P = 0.008; +300%, P < 0.001), and did not significantly decrease during 5 min recovery. The lactate ratio (erythrocytes:plasma) remained unchanged after acute exercise pre-training, but was significantly increased after 5 min recovery post-training (compared with the resting value) (+22%, P = 0.022). The results suggest an increased time-delayed influx of lactate into erythrocytes following an acute bout of exercise in endurance-trained diabetic men.

On p. 413, the text "Furthermore, accumulation … metabolism (Westerblad et al. 2002)." should read "Furthermore, the increased release of H + ions during intensive exercise (mainly due to increased ATP hydrolysis?) that is accompanied by increased lactate levels ("lactacidosis"), could be co-responsible for limiting physical performance (Gladden 2004). It has been considered that "lactacidosis" could contribute to the induction of fatigue by several mechanisms (Gladden 2004; Westerblad et al. 2002)." On p. 418, the sentence "It seems that … in the plasma." should read "It seems that an outflow of lactate from erythrocytes is possible, despite the fact that lactate levels are higher in plasma."