AJP - Regulatory, Integrative and Comparative Physiology, Vol 244, Issue 6 832-R838, Copyright © 1983 by American Physiological Society
Simultaneous determination of net uptake of 16 amino acids by a marine bivalve
D. T. Manahan, S. H. Wright and G. C. Stephens
High-performance liquid chromatography was used to measure the simultaneous
transport of 16 amino acids from seawater into the mussel Mytilus edulis.
All the substrates, including representative neutral, basic, and acidic
amino acids, were accumulated from ambient concentrations as low as 5 nM.
Influx of four radioactively labeled amino acids was compared with their
net flux. In each case the influx of the 14C-labeled substrate, determined
from the removal of isotope from test solutions, accurately represented the
net flux of that substrate as measured by direct chemical analysis. Ammonia
was the only compound observed to be routinely lost from these animals.
Rates of uptake of individual amino acids, each at concentrations of 10 nM,
ranged from 2.4 to 7.0 nmol . g dry flesh wt-1 . min-1. The studies show
that M. edulis is capable of a net uptake of dissolved amino acid from the
very low concentrations characteristic of seawater. Moreover, net
accumulation can occur against chemical gradients calculated to be in
excess of one million to one. The rates of amino acid uptake may contribute
significantly to the animals' energy requirements.
