Abstract
The effects of K+, Na+, hypo‐ and hypertonicity on the synthesis and fast axonal transport of3H‐leucine‐labelled protein were studiedin vitroin the frog sciatic system. The methodology used made it possible to discriminate between effects on synthesis and transport of protein. The preparation which consisted of the dorsal ganglia, the sciatic nerve and the gastrocnemius muscle was placed in an incubation chamber. The ganglia were incubated in standard Ringer containingSH‐leucine and the nerve was prefused with modified Ringer. Perfusion of the nerve for 17 h with K+‐free Ringer or Na+‐free Ringer did not affect the rapid axonal transport of3H‐leucine‐labelled material from the ganglia along the nerve towards a ligature in front of which it accumulated. Nor was the transport influenced by concentrations of K+up to 68.8 mM. In contrast concentrations exceeding 100 mM K+partially inhibited the transport. Inhibition by ouabain (0.1 mM) was not prevented by elevating K+to 30 mM. Deviation from isotonicity, towards a hypo‐ or a hypertonic medium, partially inhibited axonal transport. The transport inhibitory effects showed reversibility. Experimental conditions, which arrested the transport, were tested in separate experiments for effects on uptake of3H‐leucine into TCA‐soluble and insoluble ganglionic components. K+substituted for Na+, ouabain (0.1 mM) and hypotonic Ringer partially inhibited the amino acid uptake hut also subsequent steps in the incorporation process, whereas only the latter was inhibited by hypertonic Ringer. The results are discussed in relation to possible changes in energy metabolism.