The metabolism of dopamine in the blood of ruminant animals: an enzyme system to metabolize dopamine released from the mast cells in these species?

Following the i.v. administration of 3,4-dihydroxyphenylethylamine (dopamine) to sheep, 3,4-dihydroxyphenylethanol and 3,4-dihydroxyphenylacetic acid rapidly appeared in the blood. 3,4-Dihydroxyphenylethanol can be formed from dopamine by blood plasma of ruminants in vitro. It is suggested that this plasma enzyme system might serve to inactive dopamine released from mast cells in ruminant species.