Intracellular electrolytes and water analysis in dystrophic canine muscles.

Skeletal muscles from normal dogs and labrador retrievers with a hereditary muscular dystrophy were examined morphologically and histochemically and were analysed for sodium (Na+), potassium (K+) and chloride (Cl-) ions and total muscle water. The partition of total muscle water and electrolytes between intracellular and extracellular phases was calculated on the basis of the chloride space method as the estimate of extracellular fluid volume. Muscle samples from dystrophic dogs contained significantly increased concentrations of Na+, Cl-, total muscle water, and a significant reduction in the level of K+ compared with normal values. There was a significant increase in the intracellular water and Na+ levels with a concomitant reduction of intracellular K+ content. Most dystrophic muscle samples had a pronounced type 2 fibre deficiency and a marked increase in numbers of fibres with internalised nuclei.