title: Lactate influx into red blood cells from trained and untrained human subjects.
abstract: OBJECTIVE
  The purpose of this study was to compare the fractional contributions of the three pathways of lactate transport (band 3 system, nonionic diffusion, and monocarboxylate pathway) into red blood cells (RBC) from trained and untrained humans.
  
  
  METHODS
  Blood samples were obtained from 19 male subjects: 5 untrained, 5 aerobically-trained, 5 competitive collegiate cross-country runners, and 4 competitive collegiate sprinters. The influx of lactate into the RBC was measured by a radioactive tracer technique using [14C]lactate. Discrimination of each pathway of lactate transport was achieved by using PCMBS (1 mM) to block the monocarboxylate pathway and DIDS (0.2 mM) to block the band 3 system. Nonionic diffusion was calculated as the difference between total lactate influx and the sum of band 3 and monocarboxylate lactate influx.
  
  
  RESULTS
  Total lactate influx into the RBC from the more aerobic individuals (trained subjects and cross-country runners) was significantly faster at 1.6 mM lactate concentration ([La]) as compared with the influx into RBC of the untrained subjects. Total influx of lactate was significantly higher (P < 0.05) in the RBC from the sprinters as compared with that in the RBC from the untrained subjects at 41 mM [La]. There were no significant differences among the four groups with regard to the total influx of lactate at 4.1, 8.1, and 20 mM [La]. In general, the percentage of total lactate influx accounted for by each of the three parallel pathways at 1.6, 8.1, and 41.0 mM [La] was not different among the four groups of subjects.
  
  
  CONCLUSIONS
  Overall, the groups were more similar than different with regard to RBC lactate influx.
authors.affiliation: Department of Health & Human Performance, Auburn University, AL 36849-5323, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Skelton
authors.forename: D E
authors.initials: DE
authors.lastname: Kremer
authors.forename: E W
authors.initials: EW
authors.lastname: Smith
authors.forename: L B
authors.initials: LB
authors.lastname: Gladden
mesh_terms: D000328:Adult; D001692:Biological Transport / Q000502:physiology; D004912:Erythrocytes / Q000737:chemistry*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology*
chemical_list: D019344:Lactic Acid