Uf. Rasmussen et al., Aerobic metabolism of human quadriceps muscle: in vivo data parallel measurements on isolated mitochondria, AM J P-ENDO, 280(2), 2001, pp. E301-E307
Citations number
35
Categorie Soggetti
Endocrinology, Nutrition & Metabolism
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM
The aim of the present study was to examine whether parameters of isolated
mitochondria could account for the in vivo maximum oxygen uptake ((V) over
dot O-2 max) of human skeletal muscle. (V) over dot O-2 max and work perfor
mance of the quadriceps muscle of six volunteers were measured in the knee
extensor model (range 10-18 mmol O-2 . min(-1) . kg(-1) at work rates of 22
- 32 W/kg). Mitochondria were isolated from the same muscle at rest. Strong
correlations were obtained between (V) over dot O-2 max and a number of mi
tochondrial parameters (mitochondrial protein, cytochrome alpha alpha (3),
citrate synthase, and respiratory activities). The activities of citrate sy
nthase, succinate dehydrogenase, and pyruvate dehydrogenase, measured in is
olated mitochondria, corresponded to, respectively, 15, 3, and 1.1 times th
e rates calculated from (V) over dot O-2 max. The respiratory chain activit
y also appeared sufficient. Fully coupled in vitro respiration, which is li
mited by the rate of ATP synthesis, could account for, at most, 60% of the
(V) over dot O-2 max. This might be due to systematic errors or to loose co
upling of the mitochondrial respiration under intense exercise.