AJP - Endocrinology and Metabolism, Vol 251, Issue 4 393-E399, Copyright © 1986 by American Physiological Society
In vivo inhibition of tyrosine uptake into rat retina by large neutral but not acidic amino acids
M. H. Fernstrom, E. A. Volk and J. D. Fernstrom
The uptake of tyrosine into rat retina and brain was studied in vivo after
its peripheral injection alone or in combination with other amino acids.
Both retinal and brain tyrosine levels increased monotonically for at least
60 min after tyrosine administration. When tyrosine was injected along with
branched-chain amino acids, but not with acidic amino acids, such
increments in retinal and brain tyrosine levels were significantly
attenuated. The postinjection tyrosine levels in retina and brain
paralleled better the serum ratio of tyrosine to the sum of the other large
neutral amino acids (which include the branched-chain amino acids) than the
serum tyrosine level alone. These results suggest that tyrosine uptake into
rat retina, like that into brain, is mediated by a competitive transport
system shared among the large neutral amino acids.
