Some observations on the behaviour of the sodium efflux in barnacle muscle fibres towards lithium ions.
The behaviour of the Na efflux towards Li+ was studied using single barnacle muscle fibres as a preparation. It is found that the Na efflux into Li+-ASW (artificial seawater) is reduced and that this effect is not fully reversed by returning back to Na+-ASW. Preinjection of 100 mM-EGTA reduces the magnitude of the fall of the Na efflux into Li+-ASW. The remaining Na efflux into Li+-ASW is further reduced by external application of 10(-4) M-ouabain. The remaining Na efflux in ouabain-poisoned fibres is reduced by replacing Nae by Li+. However, some fibres show a rise rather than a fall. Fibres loaded with NaCl (by injection) show a prompt and sustained stimulation of the Na efflux when Nae is replaced by Li+. A similar but less pronounced response is often seen with ouabain-poisoned fibres. Injection of LiCl (e.g. a 2 M-solution), causes a 20% fall in Na efflux. Subsequent replacement of Nae by Li+ fails to bring about a fall in the remaining efflux. It is concluded that the Na efflux in these fibres consists of a Na-Na exchange diffusion component which is not mediated by the Na-K pump and that its operation is interrupted by injecting Li+. The relative size of this component is about one-fifth and not one-half of the Na efflux.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D008094:Lithium / Q000378:metabolism* / Q000494:pharmacology; D018021:Lithium Chloride; D008845:Microinjections; D009132:Muscles / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D001468:Thoracica
D002712:Chlorides; D012965:Sodium Chloride; D004533:Egtazic Acid; D010042:Ouabain; D008094:Lithium; D012964:Sodium; D018021:Lithium Chloride