Metabolic labelling and quantitation of proteins synthesized by single chick cochleas

Molecular studies of the peripheral auditory system are made difficult by the small quantities of tissue available and by their relative inaccessibility. In addition, the cochlea and other hair cell-containing receptor organs are composed of both hair cells and supporting cells, as well as several other cell types. The identification of known proteins and the characterization of specific and novel protein molecules from these tissues require the use of sensitive techniques and a consideration of the complex histology. The chick cochlea was selected as an experimental system since the cochlea is relatively accessible in the bird, the receptor neuroepithelium contains a large number of hair cells compacted in a small area, and the physiology of the auditory periphery has been studied extensively. A general procedure is described for the metabolic radiolabelling of proteins from single cochleas followed by their solubilization, separation by high-resolution two-dimensional gel electrophoresis, and accurate quantitation. The method is highly reproducible and sensitive, and should prove useful in studies of proteins from the specialized cell types of the chick cochlea, including the identification of those whose rates of synthesis are modified in response to acoustic stimulation and sound damage or recovery.