D-Methionine protects against cisplatin damage to the stria vascularis

D-Methionine (D-met) protects against cisplatin (CDDP)-induced hearing loss and outer hair cell loss (Campbell et al., 1996). However, D-met's protect ive effects on the stria vascularis has not been previously investigated. T he purpose of this study was to examine, using semi-quantitative analysis, whether D-met also protects the stria vascularis. We removed a basal turn s ection of the stria vascularis from five groups of five male Wistar rats ea ch: (1) a CDDP-treated control group receiving a 30 min i.p. infusion of 16 mg/kg CDDP, (2) a saline-injected control group receiving an equivalent vo lume of saline, and (3) three groups injected with either 75, 150, or 300 m p/kg D-methionine (D-met) i.p. 30 min prior to receiving the 16 mg/kg CDDP dosing. Using transmission electron microscopy and light microscopy, we ana lyzed strial volume (i.e. edema), marginal cell damage classification (bulg ing and/or compression), and relative optical density (ROD) ratios (i.e. de pletion of marginal cell cytoplasmic organelles). All three levels of D-met provided complete protection against marginal cell bulging and/or compress ion but only partial protection against strial edema. At 300 mg/kg, D-met s ignificantly reduced ROD ratio degradation in the spiral prominence and mid dle stria vascularis regions. In Reissner's membrane region, values from th e D-met pretreated group were not significantly different from either the t reated or untreated control groups suggesting only partial protection for t hat area. Protection of marginal cell cytoplasmic organelles was also noted . In summary, D-met partially or fully protects the stria vascularis from s everal types of CDDP-induced damage. (C) 1999 Elsevier Science B.V. All rig hts reserved.