title: Myoglobin concentration in skeletal muscle fibers of chronic heart failure patients.
abstract: The purpose of this study was to determine the myoglobin concentration in skeletal muscle fibers of chronic heart failure (CHF) patients and to calculate the effect of myoglobin on oxygen buffering and facilitated diffusion. Myoglobin concentration, succinate dehydrogenase (SDH) activity, and cross-sectional area of individual muscle fibers from the vastus lateralis of five control and nine CHF patients were determined using calibrated histochemistry. CHF patients compared with control subjects were similar with respect to myoglobin concentration: type I fibers 0.69 +/- 0.11 mM (mean +/- SD), type II fibers 0.52 +/- 0.07 mM in CHF vs. type I fibers 0.70 +/- 0.09 mM, type II fibers 0.49 +/- 0.07 mM in control, whereas SDH activity was significantly lower in CHF in both fiber types (P < 0.01). The myoglobin concentration in type I fibers was higher than in type II fibers (P < 0.01). Consequently, the oxygen buffering capacity, calculated from myoglobin concentration/SDH activity was increased in CHF: type I fibers 11.4 +/- 2.1 s, type II fibers 13.6 +/- 3.9 s in CHF vs. type I fibers 7.8 +/- 0.9 s, type II fibers 7.5 +/- 1.0 s in control, all P < 0.01). The calculated extracellular oxygen tension required to prevent core anoxia (Po2(crit)) in muscle fibers was similar when controls were compared with patients in type I fibers 10.3 +/- 0.9 Torr in CHF and 11.5 +/- 3.3 Torr in control, but was lower in type II fibers of patients 6.1 +/- 2.8 Torr in CHF and 14.7 +/- 6.2 Torr in control, P < 0.01. The lower Po2(crit) of type II fibers may facilitate oxygen extraction from capillaries. Reduced exercise tolerance in CHF is not due to myoglobin deficiency.
authors: Department of Physiology, Van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands.
authors: Martijn A
authors: MA
authors: Bekedam
authors: Brechje J
authors: BJ
authors: van Beek-Harmsen
authors: Willem
authors: W
authors: van Mechelen
authors: Anco
authors: A
authors: Boonstra
authors: Willem J
authors: WJ
authors: van der Laarse
mesh_terms: D000328:Adult; D000368:Aged; D002021:Buffers; D016022:Case-Control Studies; D002908:Chronic Disease; D017079:Exercise Tolerance; D005260:Female; D006333:Heart Failure / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism* / Q000473:pathology; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism* / Q000473:pathology; D009211:Myoglobin / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D052097:Quadriceps Muscle / Q000378:metabolism* / Q000473:pathology; D013385:Succinate Dehydrogenase / Q000378:metabolism
chemical_list: D002021:Buffers; D009211:Myoglobin; D013385:Succinate Dehydrogenase; D010100:Oxygen