Decreased protein synthesis in cochlear nucleus following developmental auditory deprivation. Use of vascular saline perfusion to improve small tissue sample analysis

The incorporation of tritiated leucine was used as an index of protein synthesis in the cochlear nucleus (CN) of mice unilaterally (right side) hearing deprived throughout the period of hearing development. Right-left differences in radiolabel concentration were measured by scintillation counting of whole tissue homogenates. To improve upon the detection of small differences in radiolabel incorporation, the brain was perfused with saline prior to removal of CN tissue and the results compared with the standard nonperfusion method of tissue collection. Statistical analyses demonstrated the perfusion significantly reduced the acid soluble (unbound) label in CN without affecting the amount of protein bound label. Furthermore, a significant right side decrease in leucine incorporation was seen with the perfusion treatment, but not in the nonperfused treatment. This demonstrated that developmental auditory deprivation led to a decrease in protein synthesis at maturity. The results also demonstrated that mechanisms for leucine uptake were not impaired and the decrease in protein synthesis was not due to reduced availability of precursor amino acid. Thus, the use of saline perfusion prior to tissue collection facilitated the identification of protein synthesis differences that were unidentified by the traditional method.