FIG. 7.

Effect of sodium nitroprusside-produced nitric oxide on HeLa and McCoy cells (A and B) and on the growth of C. trachomatis L2 (C) and C. muridarum (D) in HeLa and McCoy cells. HeLa and McCoy cells were infected with chlamydiae and then cultured in the appropriate complete medium (Table 1) plus the indicated concentration of SNP. After culturing for 48 h, medium nitrite levels were determined using the Griess reagent, host cell cytotoxicity was measured by assaying medium lactate dehydrogenase activity, and chlamydia growth was assessed by titrating recoverable IFU. Growth data are presented as IFU (log₁₀) and represent the means ± standard errors of triplicate determinations. See the legend to Fig. 1 and Materials and Methods for details. Medium nitrite levels were determined after 48 h of incubation using the Griess reagent. Data are presented as μM nitrite and represent the means of two independent experiments with ranges shown.