IMMUNOCYTOCHEMICAL LOCALIZATION OF SALIVARY PEPTIDE P-C IN HUMAN SUBMANDIBULAR-GLAND

Human saliva contains a proline-rich polypeptide, salivary peptide P-C , which potentiates insulin release and reduces glucagon release from perfused rat pancreas to decrease blood glucose level, To elucidate th e process of secretion into humoral fluid of this peptide morphologica lly we investigated ultrastructural localization of P-C in human subma ndibular gland by immunogold technique with anti-peptide P-C whose spe cificity to P-C mas confirmed bq. immunoblotting. The labeling with go ld particles which represents the distribution of P-C-like-immunoreact ivity (P-C-LI) mas detected in the secretory granules and rough endopl asmic reticula of the acinar serous cells and in few mucosa cells. P-C -LI was also observed in the lumen of striated duct but not intracellu larly in the ductal cells themselves, indicating that P-C is not proba bly reabsorbed there, These results suggest that salivary peptide P-C is present in acinar serous cells, is secreted into the oral cavity an d may be reabsorbed through the digestive tract to modulate the blood glucose level after feeding.