Diffusion of myoglobin in skeletal muscle cells — dependence on fibre type, contraction and temperature

Abstract

We measured the diffusion coefficient of myoglobin (D _Mb) inside mammalian skeletal muscle cells with a microinjection technique. A small bolus of horse Mb was injected into a single muscle fibre and the subsequent time-dependent changes of the Mb profiles along the fibre axis were measured with a microscope-photometer. For fibres of the rat soleus muscle at 22° C, a D _Mb of 1.3·10⁻⁷ cm²/s was found, confirming a result obtained previously by us for rat diaphragm muscle with a photo-oxidation technique. In the extensor digitorum longus muscle of the rat, a higher value of 1.9 · 10⁻⁷ cm²/s was measured. Auxotonic muscle contractions did not change the apparent D _Mb. For the temperature range between 22 ° C and 37 ° C, a temperature coefficient, Q ₁₀, of 1.5 was calculated. The implication of this result for the role of Mb in the facilitation of oxygen transport was examined. Model calculations show that with this relatively low D _Mb value, the intracellular oxygen supply can be improved only slightly.