Plasma dopa and feeding.
Dopa is a normal constituent of plasma in man and experimental animals. Dopa concentrations in plasma have been used to reflect the activity of tyrosine hydroxylase, the rate-limiting enzyme in the synthesis of catecholamines. However, it is not known to what extent plasma dopa is affected by feeding, since several foods contain dopa or tyrosine, the immediate precursor of dopa. In this study dopa and its major metabolites (3-O-methyldopa and free and conjugated catecholamines) were measured in plasma of dogs during 5 hr after feeding. Plasma dopa did not change significantly after feeding. This finding increases the value of plasma dopa as an index of tyrosine hydroxylase activity. Plasma norepinephrine decreased, and conjugated dopamine increased, after feeding; the other analytes did not change significantly.
Banwart
B
B
Department of Physiology and Biophysics, Mayo Clinic, Rochester, Minnesota 55905.
Miller
T D
TD
Jones
J D
JD
Tyce
G M
GM
D000821:Animal Feed / Q000032:analysis; D000818:Animals; D004295:Dihydroxyphenylalanine / Q000032:analysis / Q000097:blood*; D004285:Dogs; D004298:Dopamine / Q000378:metabolism; D004435:Eating; D004837:Epinephrine / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D013997:Time Factors; D014443:Tyrosine / Q000031:analogs & derivatives / Q000097:blood
D014443:Tyrosine; D004295:Dihydroxyphenylalanine; C008404:3-methoxytyrosine; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine