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Metachromasia as the key to aminoglycoside ototoxicity. Preliminary report
Abstract:
In in-vitro experiments, it was shown that aminoglycosides, in contrast to other antibiotics, inhibited the metachromatic reaction using o-toluidine blue as a basic dye and heparin-Na as a polysulfate-polysaccharide substrate. The inhibitory concentrations were inversely proportional to the free amino groups of aminoglycosides tested. Taking into consideration (a) that the aminoglycosides antagonize the presence of Ca++ and (b) that mechanisms of ototoxicity involve ionic alterations in endolymph, we suggest that: aminoglycoside ototoxicity could be the result of the reaction between aminoglycosides and anionic polyelectrolytes, of the group of polysulfated polysaccharides, in a metachromatic process.
Insights
Aminoglycoside antibiotics inhibit a specific dye reaction, unlike other antibiotics. This inhibition, linked to their chemical structure, may explain their ototoxicity by interfering with essential bodily electrolytes.
Area of Science:
- Biochemistry
- Pharmacology
- Ototoxicology
Background:
- Aminoglycosides are a class of antibiotics with known ototoxic side effects.
- The mechanisms underlying aminoglycoside-induced ototoxicity are not fully elucidated but involve ionic alterations in the inner ear's endolymph.
Purpose of the Study:
- To investigate the interaction between aminoglycosides and anionic polyelectrolytes.
- To explore a potential mechanism for aminoglycoside ototoxicity based on in-vitro observations.
Main Methods:
- In vitro experiments utilizing o-toluidine blue as a basic dye.
- Heparin sodium (heparin-Na) was employed as a polysulfated polysaccharide substrate.
- Measurement of the inhibitory concentrations of various aminoglycosides on the metachromatic reaction.
Main Results:
- Aminoglycosides, distinct from other antibiotics, inhibited the metachromatic reaction.
- The degree of inhibition correlated inversely with the number of free amino groups on the tested aminoglycosides.
- Observed antagonism of Ca++ by aminoglycosides was noted.
Conclusions:
- Aminoglycoside ototoxicity may stem from their reaction with anionic polyelectrolytes, such as polysulfated polysaccharides, via a metachromatic process.
- This interaction, potentially involving ionic alterations, offers a plausible explanation for the observed ototoxic effects.
