Phagocytosis in Rat Peritoneal

C o n t r a r y to previous reports, commercially available 1000-nm latex beads were found to be labelable with 12sI, yielding a product that retained its radiolabel on storage at 4~ and when incubated in tissue-culture media. This finding permitted a radiochemical method to measure phagocytic uptake of latex particles by rat peritoneal macrophages cultured in vitro, and a direct compar i son with the established method of particle counting by light microscopy. The two methods yielded c lose ly s imilar da ta , demonstrating that the (much more convenient) radiochemical method for quantitating phagocytic uptake is both feasible and reliable. The kinetics of phagocytic uptake of the latex particles and the ef fect of low temperature and metabolic inhibitors (sodium fluoride and 2,#-dinitrophenol) are described. Ongoing phagocytosis did not alter the rate of fluidphase pinocytosis by macrophages.