Immunohistochemical localization of chromogranin a in the acinar cells of equine salivary glands contrasts with rodent glands.

We investigated the existence of chromogranin A (CgA) in salivary glands of the horse by Western blotting and enzyme immunoassay (EIA) using an antiserum against a peptide sequence of equine CgA. We also compared its cellular distribution between the horse and rat salivary glands with a tyramide signal amplification immunofluorescence technique. Western blotting gave three significant immunoreactive bands (74, 56 and 48 kDa) in adrenal medulla and three major salivary glands of horses. Immunoreactivities for CgA measured by EIA in horses were 154.05 +/- 41.46, 20.32 +/- 5.59 and 4.43 +/- 2.23 pmol/g wet weight in the parotid gland, submandibular gland and sublingual gland, respectively, and 1.03 +/- 0.407 pmol/mg protein in the saliva. Immunohistochemically, the positive reactivity was mainly recognized at acinar cells in equine salivary glands. This exhibits a contrast to the finding in the rat salivary glands that the CgA immunoreactivity is localized at the duct cells of the submandibular gland. These results provide novel evidence that in the horse, CgA is stored in the acinar cells of salivary glands, and secreted into saliva.