title: Radioactive labeling of phospholipids and proteins by cochlear perfusion in the guinea pig and the effect of neomycin.
abstract: Phospholipids and proteins of guinea pig stria vascularis, spiral ligament and organ of Corti were radioactively labeled by perilymphatic perfusion with artificial perilymph containing [32P] orthophosphate or radioactive amino acids. Phospholipids were separated by thin-layer chromatography, proteins by disc gel electrophoresis and quantitated by liquid scintillation counting. The addition of 10-4M to 10-2M neomycin to the perfusion fluid resulted in a dose-dependent increase of tissue permeability to the radioactive precursors, and a specific decrease in the 32P-incorporation into phosphatidylinositol diphosphate in stria vascularis and organ of Corti. No effect of neomycin on protein labeling was observed using a double label approach with [3H]methionine and [35S]-methionine. In vitro, low concentrations of neomycin led to the formation of a complex and polyphosphoinositides. Much higher concentrations of the drug were needed for a comparable reaction with the acid mucopolysaccharide, chondroitin sulfate A. The implications of these findings for the mechanism of neomycin ototoxicity are discussed.
mesh_terms: D000818:Animals; D003051:Cochlea / Q000378:metabolism* / Q000502:physiology; D006168:Guinea Pigs; D006801:Humans; D007553:Isotope Labeling; D009355:Neomycin / Q000494:pharmacology*; D009925:Organ of Corti / Q000378:metabolism; D010477:Perfusion; D010743:Phospholipids / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D011506:Proteins / Q000378:metabolism*
chemical_list: D010743:Phospholipids; D010761:Phosphorus Radioisotopes; D011506:Proteins; D009355:Neomycin