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

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.

Both salt adaptation and immersion for 2 – 3 days in 5 × 1⁻⁴ M amiloride in tap water resulted in a decrease in blood pH (from 7·720 ± 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).

In vitro determination of Na⁺/H⁺ 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 salt-adapted toads and the uptake of sodium was reduced.