Effect of muscle mass on lactate formation during exercise in humans.
To elucidate the mechanisms of lactate formation during submaximal exercise, eight men were studied during one- (1-LE) and two-leg (2-LE) exercise (approximately 11-min cycling) using the catheterization technique and muscle biopsies (quadriceps femoris muscle). The absolute exercise intensity and thus the energy demand for the exercising limb was the same [mean 114 (SEM 7) W] during both 1-LE and 2-LE. At the end of exercise partial pressure of O2 and O2 saturation in femoral venous blood were lower and arterial adrenaline and noradrenaline were higher during 2-LE than during 1-LE. Mean arterial blood lactate concentration increased to 10.8 (SEM 0.8) (2-LE) and 5.2 (SEM 0.4) mmol.l-1 (1-LE) after 10 min of exercise. The intramuscular metabolic response to exercise was attenuated during 1-LE [mean, lactate = 49 (SEM 9); glucose 6-P = 3.3 (SEM 0.3); nicotinamide adenine dinucleotide, reduced = 0.17 (SEM 0.02); adenosine 5'-diphosphate 2.7 (SEM 0.1) mmol.kg dry mass-1] compared to 2-LE [76 (SEM 6); 6.1 (SEM 0.7); 0.21 (SEM 0.02); 3.0 (SEM 0.1) mmol.kg dry mass-1, respectively]. To elucidate whether the lower plasma adrenaline concentration could contribute to the attenuated metabolic response, additional experiments were performed on four of the eight subjects with infusion of adrenaline during 1-LE (1-LEE). Average plasma adrenaline concentration was increased during 1-LEE and reached 2-4 times higher levels than during 2-LE. Post-exercise muscle lactate and glucose 6-P contents were higher during 1-LEE than during 1-LE and were similar to those during 2-LE.(ABSTRACT TRUNCATED AT 250 WORDS)
Jensen-Urstad
M
M
Department of Clinical Physiology, Södersjukhuset, Karolinska Institute, Stockholm, Sweden.
Svedenhag
J
J
Sahlin
K
K
D000227:Adenine Nucleotides / Q000378:metabolism; D000328:Adult; D004734:Energy Metabolism / Q000502:physiology; D004837:Epinephrine / Q000097:blood; D015444:Exercise / Q000502:physiology*; D006600:Hexosephosphates / Q000378:metabolism; D006801:Humans; D007773:Lactates / Q000096:biosynthesis*; D019344:Lactic Acid; D007866:Leg / Q000502:physiology; D008297:Male; D009132:Muscles / Q000033:anatomy & histology* / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology; D012119:Respiration / Q000502:physiology
D000227:Adenine Nucleotides; D006600:Hexosephosphates; D007773:Lactates; D019344:Lactic Acid; D004837:Epinephrine