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MECHANISM OF EXTRACELLULAR POTASSIUM STIMULATION OF PROTEIN SYNTHESIS IN THE IN VITRO HIPPOCAMPUS 1
Author(s) -
Lipton Peter,
Heimbach Catherine J.
Publication year - 1978
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1978.tb06255.x
Subject(s) - extracellular , ouabain , protein biosynthesis , amino acid , intracellular , potassium , biochemistry , biophysics , stimulation , hippocampal formation , in vitro , biology , chemistry , sodium , endocrinology , organic chemistry
Transverse slices of guinea‐pig hippocampus respond to small increases in extracellular potassium concentration [K + ] by showing a marked augmentation in the rate of incorporation of labelled precursor amino acid into protein. We find that this augmentation is manifested equally in superfusing solutions containing low specific activity/high concentration precursor and high specific activity/low concentration precursor. This provides additional evidence that the effect of extracellular [K + ] is on the rate of protein synthesis and not on the precursor pool. Extracellular [K + ] augments amino acid incorporation normally in the presence of concentrations of α‐amanatin and actinomycin D which are inhibiting RNA synthesis by over 97%. This suggests the effect is exerted post‐transcriptionally. Extracellular [K + ] causes an unattenuated increase in protein synthesis in the presence of high Mg 2 + (20m m ) or low Ca 2+ (0 m m ) in the superfusate–suggesting this effect of [K + ] does not result from an effect on neurotransmitter release. Increases in extracellular [K + ] which increase protein synthesis threefold (1.3‐6.4m m ‐K + ) increase the intracellular [K + ]/[Na + ] 2‐fold. 3 x 10 ‐7 m ‐Ouabain. which lowers incorporation by 40‐50% lowers [K + ]/[Na + ] by about 50% while having no effect on the uptake of labelled precursor or on the cell concentrations of ATP. These results suggest that protein synthesis in the cell is sensitive to [K. + ]/[Na + ] and that an alteration in this ratio is the mechanism by which the concentration of extracellular [K + ] affects the rate of in vitro hippocampal protein synthesis. This effect of extracellular [K + ] on synthesis is not observed in slices from non‐cerebral organs of the guinea pig.