Quantitative reduction of 2,3,4-triphenyl tetrazolium chloride by hamster trachea organ cultures: effects of Mycoplasma pneumoniae cells and membranes

Abstract

The ability of Mycoplasma pneumoniae cells and membranes to affect tetrazolium reduction by hamster trachea organ cultures was evaluated. Uninfected trachea explants reduced 2,3,5-triphenyl tetrazolium chloride (TTC) and nitro-blue tetrazolium when incubated at 37 C in the absence of air. Reduced tetrazolium salts (formazans) were extractable with acetone or ethylene glycol and could be quantitated spectrophotometrically. The optimal assay system involved the use of three or more tracheal rings incubated for 2 h in 0.12% TTC in Tyrode balanced salts supplemented with 1.2% sodium succinate. Formazan was extracted for 5 min with acetone, and the optical density (490 nm) was determined. Trachea explants with metabolic activity reduced or obliterated by freeze-thaw lysis, heat (56 C X 30 min), or cyanide (0.1 M NaCN X 30 min) had negligible ciliary activity and tetrazolium reduction activity (optical density at 490 nm [dry weight]). Tracheas exposed to mycoplasma cells or membranes also showed significantly decreased ciliary activity and tetrazolium reduction; e.g., only 5pc of the ciliary activity and reduction capacity remained after 5 days in culture when infected with M. pneumonia PI 1428 cells. The data indicate that the exposure of ciliated respiratory epithelium to mycoplasma cells or membranes results in diminished oxidative metabolism, and that the ability to reduce TTC to its formazan is correlated with relative ciliary activity.