TRASPORTO DELL'OSSIGENO NELL'UOMO ALLE ALTE QUOTE. III. CONTRIBUTO DELLA MIOGLOBINA ALLA DIFFUSIONE DELL'OSSIGENO NELLA FIBRA MUSCOLARE

Translated title of the contribution: Oxygen transport in men at high altitudes. III. Role of myoglobin in oxygen diffusion in muscle fiber

P. Ascenzi, G. Amiconi

Research output: Contribution to journalArticle

Abstract

An adequate O 2 supply to the mitochondria of the skeletal muscles depends on both the partial O 2 pressures in the capillaries and the myoglobin concentration in the muscular fibre. The myoglobin concentration is constant in the cardiac muscle of all adult mammals; on the contrary, in the skeletal muscles it undergoes variation depending on the adaptation to low O 2-pressure or to increased metabolic demand induced by physical training. The myoglobin operates in a state of partial deoxygenation, this implies an oxygen gradient bound to the protein and progressing from the periphery to the axis of the fibre. The same gradient, which has a slope depending on the shape of the dissociation curve of myoglobin-O 2, is very necessary for the contribution of myoglobin to maintain an O 2 flux from capillaries to mitochondria. In fact, the O 2 molecules diffuse through the muscle in any direction whether free or transported by the movements of the protein molecules. Since a gradient of concentration exists, the statistical results of such a process corresponds to the sum of the diffusion flux of the free O 2 and the diffusion flux of the myoglobin-bound O 2. Such a physiochemical phenomenon, i.e. the O 2 diffusion facilitated by myoglobin, has been treated in terms of both translational diffusion of the O 2 molecules bound to the protein and the dissociation rate of O 2 from the myoglobin-oxygen complex. The assumption according to which a chemical equilibrium exists in each point of the muscular fibre, allows the development of a simple equation from which can be calculated the facilitated O 2-diffusion in the muscle; in addition it is possible to conclude that myoglobin is responsible for the O 2 intramolecular transport, specially when the pressure of the gas is low. The contribution of rotational diffusion of myoglobin to the phenomenon of O 2 transport facilitated by this hemoprotein as well as the reserve function of this protein in man are neglible.

Translated title of the contributionOxygen transport in men at high altitudes. III. Role of myoglobin in oxygen diffusion in muscle fiber
Original languageItalian
Pages (from-to)153-163
Number of pages11
JournalMedicina dello Sport
Volume34
Issue number3
Publication statusPublished - 1981

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Public Health, Environmental and Occupational Health
  • Physical Therapy, Sports Therapy and Rehabilitation

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