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

Abstract

SUMMARY1. 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 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 mM-K, there was little or no rise in the Na efflux. Raising the external K to 50 or 100 mm caused a marked rise in the Na efflux. Raising the external K to 30 mm in the absence of external Ca2+ 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 mM-CaCl2 often caused a significant rise in the Na efflux.8. Internal application of 2x5 or 5 M saline caused a prompt and large t Permanent address: Institute of Physiology and Medical Biophysics, University of Uppsala, Uppsala, Sweden. E. EDWARD BITTAR AND OTHERS 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-MgCl2. 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.

Stimulation by high external potassium of the sodium efflux in barnacle muscle fibers

“…Earlier work showed that exposure of barnacle muscle fibers (isolated from Monterey Bay specimens) to 30 mM K stimulates the Na efflux in ouabain-treated and untreated fibers (Danielson et al, 1971;Bittar et al, 1972). This work has been confirmed (Bittar et al, 1973).…”

“…Bittar et al (1972) reported that the Na efflux in fibers isolated from Monterey Bay The effect of Na+-free ASW on the response of the ouabain-insensitive Na efflux to 100 mM K. (B): The effect of varying external Na § on the response of the ouabain-insensitive Na efflux to 100 mM K. The ordinate is the average maximum rate constant for the stimulated Na &flux relative to that measured separately in control experiments using normal (100%) Na § The number of observations made at each concentration tested is indicated in parenthesis. Vertical bars indicate • sE~ specimens is stimulated even when external Ca z + is removed.…”

The effect of lowering external sodium on the intracellular sodium activity of crab muscle fibres.

“…However, it must also be noted that ai a did not rise significantly in any of the fibres and so possibly the interfibre spaces were still not completely K-free even though, in the experiment shown, the fibre was superfused with 0 KO for over 50 min, causing a hyperpolarization of the membrane potential of over 20 mV. Nevertheless, experiments on the Na pump in Maia and giant barnacle fibres, using radiotracers and Na-loaded muscles have indicated that 0 Ko can halve Na-pumping into normal Ringer within 10-20 min 249 R. D. VA UGHAN-JONES (Bittar, Caldwell & Lowe, 1967;Brinley, 1968;Bittar, Chen, Danielson, Hartmann & Tong, 1972 In two other experiments, treatment with 2 x 104 M ouabain for about an hour caused aNa to rise by about 2 and 1 m-mole/hr, and in the fourth experiment 10-5M ouabain caused no rise whatsoever of apla over a 40 min period. In all experiments there was no substantial reduction in the response to low Nao.…”

The influence of injected cyclic AMP protein kinase catalytic subunit on the sodium efflux in barnacle muscle fibres

“…Single muscle fibres were isolated by dissection from the depressor muscle bundles and cannulated, as previously described (Bittar, Chen, Danielson, Hartmann & Tong, 1972). The fibres used were 3-5 cm in length and 1-2 mm in width.…”