The authors studied the effect of indomethacin and naproxen on the changes of renal prostaglandin E and F_{2 alpha} concentration in experimental kidney infection, as well as the action of arginine-vasopressin in healthy rats. Naproxen proved to be an effective inhibitor of prostaglandin synthesis, as did indomethacin. In control animals an increased prostaglandin E and F_{2 alpha} synthesis was observed caused by arginine vasopressin. It is supposed that ADH — depending on its concentration — has a metabolic modulator role in prostaglandin synthesis, which raises the possibility of a self-regulatory mechanism of water reabsorption.