[Distribution of sodium and potassium in avian skeletal muscles]

Studies have been made on the peculiarities of distribution of Na+ and K+ in functionally different skeletal muscles of 6 species of birds. Comparison of tissue concentration ratio K+/Na+ as well as of distribution coefficients of these ions in tissue and the external medium revealed that selectivity of muscles to K+ and Na+ is related to functional specialization of the contractile mechanism. Dynamic contractile parameters in avian muscles were studied. It was shown that distribution coefficient of K+ and Na+ in muscles is quantitatively related to the velocity of development of isometric contraction. The described dependence between the ionic selectivity of muscle and their morpho-functional characteristics corresponds to the general pattern of this dependence established for skeletal muscles of other Vertebrates.