Infection with Mycobacterium tuberculosis induces apoptosis in murine macrophage lines. Resistant macrophages B10R (Bcg(r)) are more prone to undergo apoptosis than susceptible BIOS (Bcg(s)) macrophages. Apoptosis and inhibition of intracellular growth of the mycobacteria seem to be dependent on the production of nitric oxide, since both can be reverted by aminoguanidine (AMG). Although B10R macrophages produce more superoxide anion than BIOS macrophages after infection with M. tuberculosis, reactive oxygen intermediate (ROIs) scavengers did not affect uptake of H-3-uracil incorporation by the mycobacteria nor the induction of apoptosis, These results further suggest that both phenomena are dependent on the production of nitric oxide by the infected macrophages. (C) 1998 Academic Press.