Free and conjugated plasma catecholamines, DOPA and 3-O-methyldopa in humans and in various animal species.
The aim of the present study was to determine the extent to which plasma catecholamines are conjugated in different animals compared to man and how widespread is the presence of dihydroxyphenylalanine (DOPA) and 3-methoxy-4-hydroxyphenylalanine (3-OMD) in plasma among the different animal species. Free and conjugated norepinephrine, epinephrine, and dopamine were measured in plasma in humans and in several animal species (dog, rat, Gunn rat, cat, rabbit, guinea pig, African green monkey, young pig, calf, and one American black bear) using HPLC with electrochemical detection. The same technique was used to measure free and conjugated DOPA and 3-OMD in plasma of man, dog, rat, Gunn rat, calf, and American black bear. Human plasma contains the highest concentration of total (free and conjugated) catecholamines (46.1 pmole/ml), while low concentrations (below 15 pmole/ml) were observed in unstressed rats, calves, cats, and young pigs. In man, 95.3% of total plasma catecholamines were conjugated. The extent to which plasma catecholamines were conjugated varied greatly between animal species. The conjugated fraction expressed as percentages of the total catecholamines is lowest in the young pig (4.7%) and highest in the bear (100%). Conjugated dopamine was present in the plasma of all species, varying between 3% of the total catecholamine pool in young pig to 90% in dog. Conjugated norepinephrine was also present in plasma of all species except in unstressed rats with access to food. Conjugated epinephrine was detected only in cat and rat. Free DOPA and 3-OMD were present in plasma of all tested species with especially high levels of 3-OMD being present in dog. Conjugated DOPA and 3-OMD were not consistently found in any species. Our results indicate that man, dog, bear, and African green monkey are particularly good catecholamine conjugators and that young pig, guinea pig, rabbit, and calf are poor conjugators.
D000328:Adult; D000818:Animals; D002395:Catecholamines / Q000097:blood*; D002415:Cats; D002417:Cattle; D002522:Chlorocebus aethiops; D004295:Dihydroxyphenylalanine / Q000097:blood*; D004285:Dogs; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D008297:Male; D008875:Middle Aged; D011817:Rabbits; D051381:Rats; D011911:Rats, Gunn; D011919:Rats, Inbred Strains; D013045:Species Specificity; D013552:Swine; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000097:blood; D001503:Ursidae
D002395:Catecholamines; D014443:Tyrosine; D004295:Dihydroxyphenylalanine; C008404:3-methoxytyrosine