The Effect of Salt Adaptation and Amiloride on the in Vivo Acid-base Status of the Euryhaline Toad Bufo Viridis

1. The acid-base status of the blood of the toad Bufo viridis was studied during adaptation to high salinity and in tap water containing amiloride. 2. Both salt adaptation and immersion for 2-3 days in 5 x io" M amiloride in tap water resulted in a decrease in blood pH (from 7720 ± 0-026 in tap water to 7-4561 0-051 in 500 mOsm NaCl-adapted toads; mean ± S.E.), and a simultaneous decrease in the concentration of HCO3~ (from 17-8 ±1-4 in tap water to 9-5 ± 1-2 in salt-adapted toads). 3. In vitro determination of Na^r l^ exchange across the skin showed a 1:1 relation in skins from tap-water-adapted toads; this exchange was inhibited by amiloride. H+ secretion was abolished in skins from saltadapted toads and the uptake of sodium was reduced.