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

This research looks into the presence of a protein called chromogranin A (CgA) in horse salivary glands. Its storage and secretion from the salivary glands are in the acinar cells, unlike in rats where it’s found in the ductal cells.

Methods

• The researchers used Western blotting and enzyme immunoassay (EIA) to determine if CgA was present in horses’ salivary glands. These techniques used an antiserum against a peptide sequence specific to equine CgA.
• They compared the distribution of CgA in horse and rat salivary glands through an immunofluorescence technique known as tyramide signal amplification (TSA).

Results

• The testing revealed three significant immunoreactive bands in both the adrenal medulla – the inner part of the adrenal gland – and the three major salivary glands (parotid, submandibular, and sublingual) of horses. These bands, with weights of 74, 56, and 48 kDa, indicate the presence of CgA.
• More specifically, they measured the immunoreactivity of CgA in horse by EIA. The values were highest in the parotid gland, followed by the submandibular and sublingual glands, and was lowest in the saliva.
• Immunohistochemical detection showed positive CgA reactivity mainly in the acinar cells of horse salivary glands. This contrasts the findings in rats where CgA is mostly localized in the duct cells of the submandibular gland.

Conclusion

• The findings provide evidence indicating that in horses, CgA is stored in the acinar cells of the salivary glands, different from its storage location in rats. From here, it is secreted into the saliva.

Significance

• The differences in localization of CgA between species highlight the importance of comprehensive interspecies studies before applying findings to other species. This is of particular relevance in areas such as drug development where animal models often serve as the first step.