DISTURBANCE OF REGULATION OF SODIUM BY CIS-DIAMMINEDICHLOROPLATINUM IN PERILYMPH OF THE GUINEA-PIG COCHLEA

We studied the acute effects of cis-diamminedichloroplatinum (CDDP) on the cochlear partition and inner ear fluid in the guinea pig. At 48 h ours after the administration of a r;ingle intramuscular injection of CDDP, 12.5 mg/kg of body weight, the endocochlearresting potential (EP ) was significantly decreased to 32.1 +/- 1.8 mV in the treated animal s, versus 80.6 +/- 1.0 mV in the control animals. There was a signific ant rise in potassium (K+), sodium (Na+), and chlorine (Cl-) in the en dolymph of the animals treated with CDDP as compared with the control animals. Only Na+ was found to increase significantly in the perilymph , reaching more than twice the level of the control animals; both K+ a nd Cl- remained within the normal range. Serum electrolytes also remai ned within the normal range. Evaluation of modified ionic permeabiliti es across the endolymph-perilymph barrier showed an apparent increase in Na+ permeability and a normal range of K+ and Cl- permeabilities. H istopathologic examination of the cochlea showed a moderate collapse o f the endolymphatic space, with atrophy of the stria vascularis and de struction of the outer hair cells. The findings suggest that the acute changes produced in the cochlea by administration of CDDP were attrib utable to a breakdown in the regulation of Na+ metabolism in the peril ymph.