Effect of osmolalities comparable to those of the renal medulla on function of human polymorphonuclear leukocytes

The effect of hyperosmolality on human polymorphonuclear-leukocyte (PMN) migration, aggregation, adhesion, phagocytosis, and intracellular killing of bacteria was studied to determine whether hyperosmolality comparable to that present in the renal medulla suppressed these functions directly or only as a result of inhibition of complement. Hypertonic sodium chloride or sucrose appeared to suppress migration, aggregation, and adhesion of PMNs directly, because both inhibited these functions at osmolalities that did not inactivate complement. Furthermore, it was found that leukocyte functions that were maintained in plasma freed of complement activity by chelating agents were abolished by the addition of hypertonic sucrose. Intracellular killing of bacteria was impaired by hypertonic sodium chloride, urea, or sucrose. Certain functions of leukocytes were enhanced at osmolalities of 300-400 milliosmols/kg. Aggregation, adhesion, and migration of PMNs were more sensitive to osmotic suppression than was phagocytosis, suggesting that increased susceptibility of the renal medulla to infection might result primarily from osmotic inhibition of leukocyte delivery to the site of infection.