Regulation of Mucous Acinar Exocrine Secretion with Age

Abstract

Denny and co-workers (Navazesh et al., 1992) recently reported decreased concentrations of MG1 and MG2 mucins in resting and stimulated whole human saliva with age. The current study was therefore conducted to examine whether there is a corresponding attenuation with age in stimulus secretion coupling regulating mucous cell exocrine secretion. We utilized an in vitro model system, isolated rat sublingual acini, to evaluate the regulation of mucous cell exocrine secretion. Rat sublingual glands are similar to human sublingual and minor mucous glands, both histologically and in terms of their pattern of innervation, which is predominantly parasympathetic. Mucin secretion is thus activated primarily by muscarinic cholinergic agonist and to a lesser extent by vasoactive intestinal peptide (VIP), which is co-localized with acetylcholine in parasympathetic nerve terminals. We isolated sublingual mucous acini from five-month-old and 24-month-old rats and compared the concentration responses for mucin secretion induced by VIP and the muscarinic agonist, arecaidine propargyl ester (APE). Concentration-response curves for VIP were nearly identical for mucous acini from the five-month-old and 24-month-old animals. Values for basal secretion, maximal secretion, and EC50 (approximately equal to 200 nmol/L VIP) were statistically equivalent between both age groups. Concentration-response curves for APE were also very similar between age groups, with no statistically significant difference in basal secretion or EC50 values (approximately equal to 50 nmol/L APE). Maximal secretion was slightly less but statistically different for 24-month-old vs. five-month-old animals, 158% vs. 169% above basal secretion, respectively. Collectively, we found no substantial age-related changes in the secretory responsiveness of salivary mucous cells.

Effect of the neuropeptides vasoactive intestinal peptide, peptide histidine methionine and substance P on human major salivary gland secretion

“…The appearance of the peptide‐stimulated mucous cells was similar to that in response to carbachol, also previously described in the human submandibular gland (Riva et al , ). Thus, humans belong to those species (rat, cat, dog, ferret, pig, sheep, mink and calf) in which VIP causes the acinar cells of salivary glands to lose secretory granules and to release proteins/glycoproteins, and when administered in vivo , during ongoing secretion, causes the flow rate to accelerate and the salivary protein concentration to increase (Lundberg et al , ; Inoue and Kanno, ; Reid and Heywood, ; Reid and Titchen, ; Bobyock and Chernick, ; Ekström and Tobin, , ; Tobin et al , ; Turner and Camden, ; Ekström et al , ; Culp and Richardson, ; Calvert et al , ; Ekström and Ekström, , ). So far, the rat and the mink are the only species where VIP per se , in addition, has been found to evoke an overt flow of saliva (Ekström et al , ; Tobin and Ekström, ).…”

Chromatin Stability at Low Concentration Depends on Histone Octamer Saturation Levels

“…The pelleted chromatin samples were collected and resuspended in 1Â SDS-PAGE loading dye. All samples were electrophoresed in 18% SDS gels for 2 h at 150 V. The gels were Coomassie-stained followed by a brief silver-staining enhancement (30) to compare the ratio of the core histones.…”

Salivary VIP concentrations are elevated in humans after acute stress

“…VIP was subsequently found to be co-released with acetylcholine from parasympathetic nerves and was later identified in the nervous system and endocrine systems acting as a neurotransmitter/neuromodulator (Strand, 1999, Culp andRichardson, 1996). VIP is a member of a group of regulatory peptides that include secretin and glucagon among others.…”