Vestibular histofluorescence could be due to accumulation of both the antibiotic and its derivative, streptidine, after acute streptomycin treatment in the guinea pig

Acute treatment with 300 mg/kg of pigmented guinea pigs with streptomycin s ulfate induces an elevation of endogenous fluorescence in vestibular ampull ary cristae. Fluorescence accumulates in all compartments of the epithelium , i.e., vestibular sensory and supporting cells and nerve fibers of the str oma and it was very intense I and 12 hours after its administration. Fluore scence decreased to control levels 24 hours following streptomycin injectio n. Fluorescence levels were very low either in untreated animals or in anim als injected with saline physiological solution: To investigate whether thi s fluorescence was an intrinsic property of the antibiotic or whether it wa s due to a derivative of it, or both, an in vitro fluorescence spectrum was performed with 100 muM solutions of streptomycin or streptidine, or both, dissolved in various buffer solutions at 488 nm of excitation. A discrete level of fluorescence was observed in the spectrum regardless of media when separate solutions of both streptomycin or streptidine were stu died. Fluorescence notably increased at 522-532 nm when the solutions conta ined both streptomycin and streptidine together. These results suggest that streptidine putatively derived from streptomycin may contribute to the observed fluorescence accumulation in vestibular pre parations after acute treatment. Thus, these metabolic properties of the in ner ear which transform streptomycin into streptidine, something never cons idered earlier, could be claimed as partially responsible for converting a therapeutic agent into a compound which could be as harmful as STP to the i nner ear.