Intracellular localization of salivary peptide P-C-like immunoreactivity in the human pancreatic B-cells

Abstract

Abstract. In order to clarify the intracellular localization of salivary peptide P-C-like immunoreactivity in human pancreatic B-cells, an immunohistochemical study at electron microscopic levels was carried out by the protein A-gold technique using antisera against insulin and salivary peptide P-C. Both salivary peptide P-C-like immunoreactivity and insulin-like immunoreactivity were present only in the insulin secretory granules of the pancreatic B-cells. However, the former immunoreactivity was lacking in many insulin secretory granules of foetal pancreatic B-cells while the latter immunoreactivity was seen in all insulin secretory granules. Salivary peptide P-C-like immunoreactivity was not found in the other kinds of cells in the islets. In a previous immunohistochemical study at light microscopic level, salivary peptide P-C-like immunoreactivity appeared in a few pancreatic B-cells at about the 16th week of gestation, in an increasing number during gestation, and was seen in all pancreatic B-cells a few months after birth. The present finding together with the above results suggest that absence of salivary peptide P-C-like immunoreactivity in some foetal pancreatic B-cells may be due to the underdevelopment of salivary peptide P-C-like immunoreactivity in each insulin secretory granule. From the examination of cross-reactivity of antisera against salivary peptide P-C to other kinds of salivary peptides and salivary Protein C, and from the results of an indirect immunofluorescence technique using three kinds of antisera including antisera against salivary peptide P-C, salivary peptide P-B and salivary Protein C, it was thought that salivary peptide P-C-like immunoreactivity in human pancreatic B-cells belongs neither to salivary Protein C nor to salivary peptide P-B nor to salivary peptide P-E, but either to salivary peptide P-C itself or to an unknown substance which has common antigenic determinants with salivary peptide P-C, salivary peptide P-B and salivary Protein C. Salivary peptide P-C-like immunoreactivity was not found in the pancreatic B-cells of other mammals. Thus, although a new substance other than insulin is present in the insulin secretory granules of the human pancreatic B-cells, its pathophysiological function remains unclear.

Salivary Peptide P-C Potentiates Insulin Release and Inhibits Glucagon Release from Isolated Perfused Pancreas of the Diabetic GK Rat

“…Therefore, the findings in this study suggest a close endocrine relationship between the salivary glands and the pancreas in the diabetic state. P-C derived from human saliva is localized in the insulin-secretory granules of pancreatic B cells (4). However, it has not been determined whether there is a direct link between saliva and pancreatic B cells.…”

“…From immunohistochemical studies, P-Clike immunoreactivity is found in human pancreatic B cells (3), being localized in the insulin secretory granules of these cells (4). A decrease in positive immunofluorescence due to P-C-like immunoreactivity has been reported in the pancreas of diabetic (non-insulin-dependent diabetes mellitus, NIDDM) patients (5,6).…”

Reduction of incretin‐like salivatin in saliva from patients with type 2 diabetes and in parotid glands of streptozotocin‐diabetic BALB/c mice

“…Rabbit antiserum against human salivatin was obtained from a rabbit which was immunized by an injection of bovine serum albumin (BSA)‐conjugated salivatin as previously reported[9] with minor modification. The BSA‐salivatin complex was purified by Sephadex G‐100 column chromatography and 0.5 mg of the complex was suspended in Freund's complete adjuvant and injected four times at intervals of 0, 6, 3 and 3 weeks into rabbits.…”

The Essential Amino Acid Domains in Salivary Peptide P-C That Potentiate Glucose-Induced Insulin Release and Inhibit Arginine-Induced Glucagon Release from Perfused Rat Pancreas

“…From immunohistochemical studies, P-Clike immunoreactivity was found to be localized not only in the serous cells of the salivary gland, but also in human pancreatic B cells (2), namely in the insulin-secretory granules of pancreatic B cells (3). We have reported that P-C remarkably potentiates glucose (8.3 and 16.7 mM)-induced insulin release, whereas the same concentration inhibits arginine (10 mM)-induced glucagon release in a concentration-dependent manner (4).…”