Some aspects of the inhibition of the action of antidiuretic hormone by lithium ions in the rat kidney and bladder of the toad Bufo marinus.

1. The effect of intravenous infusions of various ions on the antidiuretic action of antidiuretic hormone has been studied in rats.2. Lithium (13 mmol/l.) reversibly inhibits the antidiuretic responses. Similar concentrations of potassium, rubidium, strontium, magnesium, choline and calcium do not. Lithium has a similar effect on the antidiuretic activity of oxytocin.3. The inhibition is not simply related to blood nor whole body lithium concentrations.4. Lithium (2 mmol/l.) in contact with the serosal surface also inhibits the transport of water facilitated by either 0.5 U/l. antidiuretic hormone or 1.1 mmol/l. cyclic adenosine monophosphate in the isolated toad bladder.5. Choline (2 mmol/l.) on the serosal surface also inhibits the transport of water facilitated by vasopressin in the toad bladder.