The Use of ISMs in Working Skeletal Muscles and Venous Effluent Blood

Abstract

Even before the introduction of ion-selective microelectrodes (ISMs), it was known that K⁺ is released from contracting muscles. Loss of muscle K⁺ during contraction was described by Fenn (1936), and increased levels of K⁺ were subsequently demonstrated in the venous effluent blood by a number of authors (e.g. Kjellmer, 1965; Lind et al., 1966). Hinke (1959, 1961) was the first to employ ion-selective glass electrodes for measuring Na⁺ and K⁺ activities in muscle fibres. Since the tips of these electrodes were rather large, only giant muscle fibres could be impaled. Sorokina in 1964 succeeded in making microelectrodes selective for Na⁺ and K⁺ with tip diameters below 0.5 μm. It was not until 1972, however, that Gebert (1972) used K⁺ and Na⁺ ion-selective glass electrodes and our group (Hník, Vyskočil, Kříž and Holas 1972) used the liquid ion-exchanger potassium ISMs to measure the time course and the extent of potassium accumulation in the contracting muscles and to assess potassium losses into venous effluent blood. In 1977, Hirche reported results on K⁺ changes and Friedman (1973) and Hirche (1977) have also measured pH changes in contracting muscles with microelectrodes.