Conjugated catecholamines in birds.

Large concentrations of dopamine (DA) glucuronide were measured in the plasma of chronically cannulated adult chickens (Gallus gallus), adult ducks (Anas platyrhynchos) and 1-month-old ducklings. Glucuronides of norepinephrine (NE) and epinephrine (E) also were present but at much lower concentrations. Sulfoconjugated DA, NE and E could be detected only in chickens. There were quantitative differences between chicken and duck catecholamine metabolism: (i) glucuronoconjugates and sulfoconjugates comprised large portions of the total DA, NE and E in chicken plasma; (ii) the predominant form of DA in duck plasma was DA glucuronide while most of the NE and E circulated in unconjugated (i.e. free) form. Catecholamine levels did not differ between adult and immature ducks. Angiotensin II injection into adult ducks elicited simultaneous increases in arterial blood pressure (Pa) and free NE but did not alter conjugated catecholamine levels.