AJP - Regulatory, Integrative and Comparative Physiology, Vol 247, Issue 6 1029-R1037, Copyright © 1984 by American Physiological Society
Regulation of net amino acid exchange in sea urchin larvae
J. P. Davis and G. C. Stephens
Bacteria-free larvae of Strongylocentrotus purpuratus remove each of 14
free amino acids (FAA) from very dilute solution in seawater. When larvae
are maintained in seawater, influx of radiolabeled FAA and net removal of
substrate as determined by high-performance liquid chromatography (HPLC)
occur at the same rate in those substrates examined. Exposure of larvae to
high concentrations of glutamate, glycine, or serine (greater than 50
microM) produces large increases in these substrates in the internal pool
of FAA. After incubation of larvae in high concentrations of serine, the
rate of influx of 14C-labeled serine is decreased compared with unincubated
controls. Comparison of influx of radiolabeled serine with net change in
ambient serine as determined by HPLC indicates that the apparent change in
rate of influx is a consequence of an increase in ambient serine with time
and the resulting decrease in the specific activity of labeled serine.
Analysis of data indicates that abnormally high internal serine leads to
carrier-mediated efflux of serine as well as other neutral amino acids. The
rate of such efflux is increased in the presence of increased levels of
ambient serine.
