Suppression of leukocyte function and intracellular content of ATP in hyperosmotic condition comparable to the renal medulla.

The effects of hyperosmolality induced by high concentrations of NaCl and urea on the functions of human polymorphonuclear leukocytes was examined. Phagocytosis, intracellular killing of bacteria and superoxide production were inhibited under hyperosmotic conditions. The mechanism of the inhibition of superoxide production was different for NaCl and urea. The inhibition by NaCl was indirect and abolished at 4C and the inhibition by urea was immediate, direct and not abolished at 4C. The intracellular ATP content of leukocytes under hyperosmotic conditions induced by NaCl was significantly reduced and this reduction was abolished at 4C. On the other hand, ATP content under such conditions induced with urea was not reduced. These results suggest that the inhibition of leukocyte function by NaCl is due to an exhaustion of energy source caused by an activation of Na-K pump, and the inhibition by urea is direct inactivation of leukocytes and not due to energy exhaustion.