An investigation of sodium transport in barnacle muscle fibres by means of the microsyringe technique

• Published in: The Journal of physiology 1972-03, Vol.221 (2), p.389-414
• Main Authors: Bittar, E. Edward, Chen, Stephen, Danielson, Bo G., Hartmann, Henrik A., Tong, Edmund Y.
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - pharmacology; Animals; Anura; Biological Transport, Active; Calcium - metabolism; Calcium Chloride - pharmacology; Injections; Membrane Potentials; Methods; Microscopy, Electron; Muscles - metabolism; Myofibrils - cytology; Myofibrils - metabolism; Phosphates - pharmacology; Potassium - metabolism; Sodium - metabolism; Sodium Isotopes; Thoracica; Time Factors
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1972.sp009757

1. The cation composition of single barnacle muscle fibres following damage by axial insertion of a microsyringe has been measured. The Na and Ca contents of these fibres were raised. 2. Electronmicroscopic studies of fibres following insertion of a microsyringe indicated that the damage done resulted in tubular obstruction of the T-system. 3. Fibres loaded with radiosodium by micro-injection showed that the Na * efflux declined exponentially with time, but that in most fibres the slope ratio of d/d t ln [Na * ] 1 to d/d t (ln d[Na * ] i /d t ) was less than unity. Injections of distilled water deep in the fibre failed to influence the course of the Na * efflux. 4. K removal reduced the Na efflux by 47%. However, a few fibres displayed very little K-dependence. 5. When measured in fibres already soaked in a K-free medium for long periods the sodium efflux consisted of a brief rapid phase, followed by a slow phase of Na loss. 6. In the presence of 30 m M -K, there was little or no rise in the Na efflux. Raising the external K to 50 or 100 m M caused a marked rise in the Na efflux. Raising the external K to 30 m M in the absence of external Ca 2+ led to a rise in the Na efflux. A high K solution always caused shortening of these fibres. 7. Internal application of 1 M or 1 m M -CaCl 2 often caused a significant rise in the Na efflux. 8. Internal application of 2·5 or 5 M saline caused a prompt and large fall in the Na efflux. In the presence of high K saline-loaded fibres failed to contract. 9. Internal application of 0·5 M -ATP stimulated the Na efflux. A larger effect was not observed in fibres pre-treated with 2 M -MgCl 2 . Internal application of 0·5 M -ArP was without effect. 10. The results indicate that the barnacle fibre is a suitable preparation for the study of Na fluxes by means of the micro-injection technique. They also indicate that the mechanism regulating the Na efflux is not quite the same as that found in squid axon or frog muscle.