L-Arginine L-Aspartate

1. Some of the effects of ouabain on the absorption of 14C labeled amino acids and 32P labeled orthophosphate in squid axons have been studied. 2. ouabain in artificial seawater reduced intake of glycine, L-alanine, L-arginine, L-aspartate and L-glutamate. After a period of 3 hours in the inhibition of ouabain and glycine L-glutamate absorption was marked. 3. After 3 hours in the axoplasmic ouabain Na concentration had increased by only about 14% and the K concentration decreased only by about 9%. It is therefore unlikely that changes in Na and K gradient across the membrane due to ouabain are the reason for inhibition of amino acid uptake. This was confirmed when the axons to carry out pulses at 200 / sec for 40 minutes were made. There was no subsequent inhibition of glycine and L-glutamate absorption, although the axoplasmic Na increased by about 42% and K decreased by about 37%. 4. A detailed examination of the time course of inhibition of amino acid uptake by ouabain, were used in the intracellular Szintillatortechniken showed that there was no inhibition for 30-100 Min, then it was before fairly quickly. This operation was not affected by the cycloheximide protein synthesis inhibitor. It is unlikely that the inhibition of the orthophosphate receiving a similar delay is subjected, as has reached a maximum after 40 min. 5. It was concluded that the inhibitory effects of ouabain on amino acid uptake in squid axons are not due to effects on the sodium and potassium gradients caused by inhibition of the Na-K pump . The retardation of inhibition may reflect the operation of an intracellular regulation mechanism, which is triggered when ouabain inhibits the pump, but the time required for operation. If the formation of a second inhibitory messenger molecule is involved, it is unlikely that it is a protein.