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.

Iron deficiency in pulmonary arterial hypertension: a potential therapeutic target

“…Since myoglobin acts as an ''intracellular haemoglobin'', reducing oxygen tension in the cytoplasm and, therefore, facilitating further oxygen diffusion into the cell, low myoglobin levels could directly affect oxygen extraction and so exercise capacity. A similar hypothesis has been raised in CHF, though recent data suggested exercise intolerance in these patients was not due to myoglobin deficiency [41]. At present, it is unknown whether skeletal muscle myoglobin levels are substantially affected in iron-deficient IPAH patients.…”

Current perspectives and challenges in understanding the role of nitrite as an integral player in nitric oxide biology and therapy

“…However, proposing a biological role of pentacoordinated heme centers in stimulating NO-signaling via nitrite reduction comes with a significant problem arising from the fact that both ferrous deoxy and oxyheme react relatively rapidly (rate constants ~10 7 M -1 s -1 ) with NO to produce nitrosyl heme (Scheme 1) or nitrate respectively [29, 30]. Furthermore, the high concentrations of hemoglobin and myoglobin in red blood cells (20 mM) and cardiac/skeletal muscle (300-900 μM) [31, 32], determines that the reaction between their hemes and NO will be fast and might inhibit NO-signaling. That said, a variety of experimental evidence ranging from in vivo to isolated organ- and organelle-based studies all indicate that the combination of hypoxia, nitrite and either RBC, hemoglobin or myoglobin can stimulate NO-gas formation and / or NO-signaling.…”

Sickle Cell Disease: A Genetic Disorder of Beta-Globin

“…The genomic structure of genes encoding hemoglobin subunits, characterized by three exons and two introns, are highly similar among vertebrate animal strains [39]. Despite this, the function of some proteins belonging to the contemporary hemoglobin family in vertebrates is to store oxygen in tissues such as myoglobin, a protein formed by a globin chain, gives the red color to the muscular tissues and has structural and genomes similar to globins that form hemoglobin [37,[40][41][42][43].…”