AMINO ACID UPTAKE AND METABOLISM BY EMBRYOS

The ability of blenny Zoarces viviparus (L.) embryos in early and late development to assimilate and metabolize ambient L-alanine was investigated in vitro and in vivo by means of autoradiographic and radiochemical methods. Autoradiograms showed that after 24 h of exposure to L-[14C]alanine, label was distributed in the tissues of the embryos. Uptake rates for l4C-labelled L-alanine in vitro were estimated by measuring the disappearance of radioactivity from the medium. Net uptake rates were measured by high performance liquid chromatography of samples taken simultaneously from the medium. Uptake rates, based on uptake of the tracer (0.60^molg"1 h~'), were similar to net uptake rates (0.54^molg~ ' h"1) in embryos in late development in the in vitro incubations in 60/imol I"1 alanine. In vivo, the injected tracer was completely cleared from the ovarian fluid over 24h. After intraovarian and in vitro incubation of the embryos with labelled alanine, there was evidence for both catabolic and anabolic metabolism of the amino acid by production of I4CO2 and by incorporation of radioactivity into molecules insoluble in trichloro-acetic acid, respectively. The data provide evidence for uptake and metabolism of amino acids by embryos in vitro and in vivo. An increase in the capacity for uptake and metabolism of L-alanine may occur during development of the embryos in the ovary