Cochleotoxicity of amine groups

Abstract

It has previously been shown that polyamines are ototoxic. The relationship between the number of amine groups and ototoxicity was studied using spermine, spermidine and 1,3-diaminopropane, which are polyamines with differing numbers of amine groups. Fifty pigmented guinea pigs were studied by injecting 0.1 ml of different concentrations of spermine, spermidine or 1,3-diaminopropane intratympanically. The animals were sacrificed 4 days after the injection and the organ of Corti was studied by scanning electron microscopy. It was found that on an equimolar basis, spermine (with 4 amine groups) is more cochleotoxic than spermidine (with 3 amine groups), which is in turn more cochleotoxic than 1,3-diaminopropane (with 2 amine groups). The cochleotoxic potential of the amine groups may be a result of their cationic nature at physiological pH (7.4). This property might be part of the explanation of the ototoxicity of the aminoglycosides.