BACKGROUND: Granulocytes must migrate to the infection site, where they phagocytose the infecting agents. Their ability to migrate depends on the rheological properties of the cells, which change along with the increased viscosity of the suspension medium. The purpose of this research was to study the influence of medium viscosity on granulocyte locomotion. MATERIAL/METHODS: The random locomotion of human granulocytes was investigated by means of an assay based on direct observation of individual cell trajectories. The study was performed in viscous media, ranging from 0.7 x 10(-3) to 370 x 10(-3) Pa x s (0.7-370 cP). Hanks solution, supplemented with methylcellulose in various concentrations, was used as a medium. The locomotion of several hundred granulocytes was studied, and about 7,000 cell track-sections (steps) were recorded. RESULTS: The mean granulocyte velocity decreases slowly with increasing medium viscosity. An increase in medium viscosity of ca. 500 times results in only a three-fold reduction in velocity. Granulocytes can migrate even at the viscosity of thick honey. They are capable of overcoming resistance forces on the order of 10(-11)N. The locomotion of granulocytes in dextran and ficoll media is also described. In these media both viscosity and osmotic pressure were variable. Granulocytes stop moving at very low viscosity, on the order of 10(-3) Pa x s. CONCLUSIONS: The locomotion of granulocytes is not stopped even in media of high viscosity. The observed decrease of granulocyte velocity is comparatively small. The studies in dextran and ficoll media indicate significant influence of osmotic pressure on granulocyte locomotion.

Keywords: Granulocytes - physiology