Blood volume changes and arginine vasotocin (AVT) blood concentration in conscious fresh water and salt water adapted ducks.

Blood volume changes consisting in the removal and reinfusion respectively, of 10% of the estimated blood volume (23.2 ml on average) were induced to determine their effects on the blood concentration of arginine vasotocin (AVT), the antidiuretic hormone (ADH) of birds, in fresh water adapted ducks (water ducks) with blood osmolalities and ADH concentrations similar to those of normally hydrated mammals, and in salt water adapted ducks (salt ducks) with chronically elevated blood osmolalities and ADH concentrations. The investigations were carried out in steady state conditions, when infusion of 1 ml . min-1 of isotonic saline was matched by the excretion in water ducks and when infusion of 0.4 ml . min-1 of 1,000 mosmolal saline was matched by the salt gland excretion in the salt ducks. After blood removal, AVT blood concentration (mean +/- SE) increased from 6.5 +/- 0.4 to 8.4 +/- 0.6 pg . ml-1 in water ducks and from 18.1 +/- 1.6 to 22.6 +/- 1.9 pg . ml-1 in salt ducks. The respective blood osmolalities of 297.4 +/- 1.4 and 318.6 +/- 3.3 mOsm . kg-1 did not change. Reinfusion of the blood after steady-state conditions had been reattained decreased blood AVT from 7.9 +/- 0.7 to 6.7 +/- 0.5 pg . ml-1 in water ducks. In the salt ducks AVT concentration had already returned to the control level before blood reinfusion which induced no further reduction. The blood osmolalities remained unchanged in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)