VIII Protein Secreting Cells in the Normal Middle Ear Mucosa of the Guinea Pig: An Autoradiographic Investigation

An autoradiographic investigation was made of the middle ear secretory activity in the young guinea pig utilizing tritium-labeled leucine. A large number of secretory cells in the middle ear mucosa were distinctly labeled with isotope, suggesting they incorporate large amounts of amino acid. The maximum cell labeling occurred between one to two hours after the intraperitoneal injection of the isotope-labeled leucine. Labeling was seen as black silver grains on the microscope slides. As time progressed, the label could be traced toward the apical portion of the cell. This phenomenon could be observed in four to six hours. By 12 hours, the labeling became somewhat more diffuse throughout both the secretory cells and the ciliated cells indicating the amino acid was synthesized into solid cell constituents. However, the mucus-secreting cells in the Eustachian tube epithelium were relatively free of labeling, suggesting the goblet cells utilize a negligible amount of isotope-labeled leucine. In view of the above findings it is suggested that the middle car mucosa possesses secretory cells which take up large amounts of amino acid. This tends to indicate, therefore, that these cells are of a serous type.