The effects of lithium ions on the antidiuretic action of vasopressin in the rat.

1 The effect of intravenous infusion of lithium, 2.56 mumol/min on the antidiuretic responses to antidiuretic hormone (ADH), adenosine triphosphate (ATP), 3'-5' adenosine cylic monophosphate (cyclic AMP) and theophyline was studied in water-loaded, alcohol-anaesthetized rats. 2 Lithium reversibly inhibits the antidiuretic response to all concentrations of ADH, depressing the maximum response but not changing the amount required for half maximal response. 3 The rate of increase of serum lithium relates more clearly to the inhibitory effect than does the serum concentration. 4 Sodium concentrations in the renal papilla seem to fall when serum lithium levels are rising. 5 Lithium inhibits the antidiuretic response to ATP and cyclic AMP but does not inhibit the response to theophyline.