Endocrine Abstracts

Past studies in Pekin ducks have indicated that the sensitivity of the avian kidney to the antidiuretic action of arginine vasotocin (AVT), the avian antidiuretic hormone, differs with the osmotic status of the birds (1). The objective of this study was to determine whether this modulation involves an interaction with prostaglandins (PG's).
The study was carried-out in vivo, using 8 unanaesthetized Pekin ducks given an intravenous maintenance infusion of either 200 mosmolal saline or glucose at a rate of 1 millilitre per minute, with and without PG inhibition by indomethacin. When the birds were in steady-states of urinary output AVT was added to the infusate to deliver a dose of 0.1 nanogrammes per kilogramme per minute for 45 minutes.
In glucose infused ducks, with steady-state urinary flow rates of 0.84 plus/minus 0.11 millilitres per minute, AVT reduced the urinary outputs by 88 percent (to 0.06 plus/minus 0.10 millilitres per minute), whereas in saline infused birds, with similar steady-state urinary flow rates, the AVT caused only a 37 percent reduction (to 0.46 plus/minus 0.17 millilitres per minute). The simultaneous inhibition of PG production had no effect upon the renal response to AVT in the glucose-infused ducks, however in saline-infused animals the effect of AVT was potentiated, so that urinary fluid excretion fell by 78 percent (from 0.80 plus/minus 0.13 to 0.11 plus/minus 0.08 millilitres per minute).
These results confirm that in Pekin ducks the renal actions of AVT can be modulated by osmotic status and that this modulation involves PG production.
1. Gray et al, Br J Pharmacol 82:329-338, 1984