ANG II-induced attenuation of salt gland function in Pekin ducks is not catecholamine-dependent

Abstract

Pekin ducks (Anas platyrhynchos) were bilaterally adrenalectomized (biADX), injected with 1 mg of triamcinolone (TRIAM) kg bw(-1) im and given 0.9% saline drinking water during a 24 h recovery period followed by chemical sympathectomy with 6OH DOPA 3 h before the start of experimental observations. Baseline plasma dopamine (DA) concentrations decreased from 283 +/- 88.5 pmol ml(-1) to 42.4 +/- 11.1 pmol ml(-1); epinephrine (E) from 142 +/- 46 pmol ml(-1) to 18.4 +/- 9.2 pmol ml(-1) and norepinephrine (NE) from 742 +/- 84 pmol ml(-1) to 406 +/- 38 pmol ml(-1) 1 day after biADX + TRIAM but before chemical sympathectomy. Baseline MABP increased from 132 +/- 3.2 mmHg to 209 +/- 14.3 mmHg (P < 0.05) in response to TRIAM. After chemical sympathectomy with 6OH DOPA there was an additional 90% decrease in plasma NE to 42 +/- 9.4 pmol ml(-1) and a concurrent 60% decrease in MABP to 83.4 +/- 6.9 mmHg (P < 0.05). Nasal fluid secretion was maintained by the continuous infusion of hypertonic saline (1,000 mosmol kg H(2)O(-1) at a rate of 0.3 ml kg(-1) min(-1)). Rates of nasal fluid secretion and fluid electrolyte concentrations were unchanged following biADX + TRIAM + 6OH DOPA. Angiotensin II (ANG II; dose 1 microg kg bw(-1) i.v.), attenuated nasal fluid secretion showing that the response to ANG II was not NE- dependent. Plasma NE concentrations decreased following Tyramine i.v. (33 +/- 8.5 pmol ml(-1)) there being no vasopressor response. This is the first report of the ANG II induced attenuation of duck salt gland secretion in the absence of measurable E and NE.