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 sulfocon-jugates 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 (P_a) and free NE but did not alter conjugated catecholamine levels.