CHARACTERIZATION OF SYNTHESIS AND STORAGE OF TGF-ALPHA IN RAT PAROTIDACINAR AND INTERCALATED DUCT CELLS

Although the expression and biological role of transforming growth fac tor-alpha (TGF-alpha) have been explored in a variety of normal cells in mammalian species, little is known about the storage of TGF-alpha i n secretory cells of exocrine organs. Parotid glands from four rats we re homogenized for RNA isolation followed by reverse transcription-pol ymerase chain reaction to determine the presence of TGF-alpha message. In situ hybridization using a hamster-specific TGF-alpha riboprobe wa s done on paraffin sections. Parotid gland and isolated acinar cells w ere processed for transmission electron microscopy (TEM) and postembed ding immunogold labeled for TGF-alpha. Gold particles were counted on similar to 200 granules in 10 acinar cells and in 10 intercalated duct cells. Labeling density was calculated as the number of gold particle s per square; micrometer +/- SD. Statistical significance was calculat ed using one-way analysis of variance. Using multiple technologies, we have established that rat parotid acinar and intercalated duct cells synthesize TGF-alpha and store the precursor form of this cytokine in their secretory granules.