Comparative effect of the naphthalenic ansamycins rifamycin SV, rifampin and cyclopentylrifampicin on murine neutrophil function.

The purpose of this study was to evaluate the in vitro effect of the naphthalenic ansamycins rifamycin SV, rifampin and cyclopentylrifampicin on neutrophil degranulation and cytokinesis using murine peritoneal exudate cells. It was found that the FMLP-stimulated secretion of myeloperoxidase was significantly inhibited by 80 micrograms rifamycin SV (P less than 0.05) and cyclopentylrifampicin (P less than 0.01) per ml. Nondirected and FMLP-directed migration was significantly (P less than 0.01) inhibited by rifamycin SV and rifampin at assay concentrations above 0.31 and 5.0 micrograms/ml respectively thus confirming the low dose rifamycin effect observed by others using human neutrophils. Finally, cyclopentylrifampicin was shown to have no significant effect on nondirected or FMLP-directed neutrophil migration at assay concentrations of 1.25 to 80 micrograms per ml.