Extracellular pH defense against lactic acid in normoxia and hypoxia before and after a Himalayan expedition

Abstract

The extracellular pH defense against the lactic acidosis resulting from exercise can be estimated from the ratios -delta[La].delta pH-1 (where delta[La] is change in lactic acid concentration and delta pH is change in pH) and delta[HCO3-].delta pH-1 (where delta[HCO3-] is change in bicarbonate concentration) in blood plasma. The difference between -delta[La].delta pH-1 and delta[HCO3-].delta pH-1 yields the capacity of available non-bicarbonate buffers (mainly hemoglobin). In turn, delta[HCO3-].delta pH-1 can be separated into a pure bicarbonate buffering (as calculated at constant carbon dioxide tension) and a hyperventilation effect. These quantities were measured in 12 mountaineers during incremental exercise tests before, and 7-8 days (group 1) or 11-12 days (group 2) after their return from a Himalayan expedition (2800-7600 m altitude) under conditions of normoxia and acute hypoxia. In normoxia -delta[La].delta pH-1 amounted to [mean (SEM)] 92 (6) mmol.l-1 before altitude, of which 19 (4), 48 (1) and 25 (3) mmol.l-1 were due to hyperventilation, bicarbonate and non-bicarbonate buffering, respectively. After altitude -delta[La].delta pH-1 was increased to 128 (12) mmol.l-1 (P < 0.01) in group 1 and decreased to 72 (5) mmol.l-1 in group 2 (P < 0.05), resulting mainly from apparent large changes of non-bicarbonate buffer capacity, which amounted to 49 (14) mmol.l-1 in group 1 and to 10 (2) mmol.l-1 in group 2. In acute hypoxia the apparent increase in non-bicarbonate buffers of group 1 was even larger [140 (18) mmol.l-1]. Since the hemoglobin mass was only modestly elevated after descent, other factors must play a role. It is proposed here that the transport of La- and H+ across cell membranes is differently influenced by high-altitude acclimatization.

Human muscle net K+ release during exercise is unaffected by elevated anaerobic metabolism, but reduced after prolonged acclimatization to 4,100 m

“…In accordance with these observations is the acclimatization-induced increase in muscle buffer capacity (25) and the markedly increased in vivo buffer capacity determined as ⌬La Ϫ /⌬pH in blood during exercise (4).…”

Extracellular pH defense against lactic acid in untrained and trained altitude residents

“…This is in contrast to the traditional view but confirms earlier studies of our group in altitude sojourners after descent (Böning et al 1980(Böning et al , 2001a. b nbi during recovery tends to higher values than in lowlanders (Böning et al 2007b) as well.…”

“…b bi is generally reduced by altitude effects. In the highlanders of the present study b nbi is clearly increased but not as much as in mountaineers after a Himalayan expedition (Böning et al 2001a); whether the high value in the latter is caused by more extreme altitude, the enormous rise in the proportion of young red cells or large scattering remains open. In spite of the reduced b bi the maximal pH decrease during exercise is 0.05 (UT) and 0.03 (TR) pH units, respectively, smaller in Bogotá than in Berlin caused by higher b nbi but also by a reduced D[La] and a more effective PCO 2 decrease because of the lower initial values (a given change in PCO 2 exerts a more marked effect on pH between 30 and 20 than between 40 and 30 mmHg, Siggaard-Andersen 1974).…”

“…However, there have been occasional observations that buffering is better than expected. Before and after stays at moderate or extreme altitude, Böning et al (1980Böning et al ( , 2001a calculated total extracellular buffer capacity (b) from changes (D) of lactic acid [La] concentration and pH (b = -D[La] 9 DpH -1 ) in arterialized D. Böning (&) Institute of Sports Medicine, Charité-Universitätsmedizin Berlin, Arnimallee 22, 14195 Berlin, Germany e-mail: dieter.boening@charite.de blood during ergometer tests and found a rise of b within the first week after descent. The cause was a large increase in non-bicarbonate b (b nbi ).…”

Acid?base balance at exercise in normoxia and in chronic hypoxia. Revisiting the "lactate paradox"

“…These are not quite comparable, based on changing duration, profile and extent of altitude exposure, different resting acidbase as well as electrolyte balance and hematocrit (Ht) level. In the study of Cerretelli (1976b), as pointed out by Bo¨ning et al (2001), blood lactate concentration was likely to be underestimated in respect to control data at sea level due to higher Ht (66% vs.44%) based on the 1 to 3 ratio of RBC to plasma lactate concentration (Bangsbo et al 1997). Besides, recent findings by Juel et al (2003) on erythrocytes and muscle acid-base control indicate that transport systems controlling lactate, HCO 3…”