Secretory response of dispersed rat submandibular cells. II. Mucin secretion

Abstract

The secretory response of dispersed rat submandibular cells as it relates to the secretion of D-[1-14C]glucosamine hydrochloride-labeled mucin following sympathomimetic and parasympathomimetic stimulation was evaluated. The adrenergic agonists (-)-norepinephrine and (-)-epinephrine were found to have equal efficacy and potency with a median effective concentration (EC50) of 7.1 x 10(-7) M. (-)-Isoproterenol was found to be acting as a "partial" agonist and had an EC50 of 3.9 x 10(-7) M. (-)-Phenylephrine addition resulted in a small, but significant, secretion of mucin at higher doses tested (10(-4) M--10(-3) M). Neither cholinergic nor alpha-adrenergic receptor stimulation was able to elicit a net increase in the secretion of mucin. However alpha-adrenergic receptor activation in conjunction with beta-adrenergic receptor activation facilitated the rate of secretion. Extracellular Ca2+ and Mg2+ were not required for the secretion of mucin, but extracellular Ca2+ enhanced the rate of secretion following alpha- and beta-adrenergic receptor activation. However extracellular Ca2+ did not enhance mucin secretion following beta-adrenergic receptor activation. Both cellular Ca2+ and beta-adrenergic receptor activation were required to elicit a secretory response following sympathomimetic stimulation.

Cystic Fibrosis Factors. Effect of Serum on the Secretory Response of Dispersed Rat Submandibular Cells

“…This also occurs in the dispersed rat submandibular cell preparation (23). Secretagogue-stimulated release of both mucin and K ' from these acinar cells is Ca++ dependent (23,24).…”

“…time-consuming assays such as parotid retrograde perfusion; (3) secretion by the cells closely parallels that found in vivo, yet diffusion problems and complex cellular interactions are obviated; (4) the secretory response is quantitative, rapid, and reproducible; (5) there exists a broad description of the major features of the secretory process which includes secretagogue receptors and their dose response to specific agonists, kinetics of net K+ and Na+ transport and much release, and the requirement for divalent cations (23)(24)(25).…”

“…In this gland and other exocrine glands, a-adrenergic and muscarinic cholinergic agonists as well as certain polypeptides are known to stimulate secretory activity (IS, 20,21,25,26). An early event associated with this stimulation is the marked and rapid change in membrane permeability to K+ (18,20,23,26,27,30), and the release of intracellular K' by these secretagogues is dependent upon extracellular Ca" (21,22,24,27,30). The dispersed submandibular gland preparation thus allows, in a single bioassay, the search for C F factor(s) which modify acinar cell receptor response to secretagogues, which alter the distinct ion channels involved in cation efflux and re-entry, or which effect changes in Ca" homeostastis in these cells.…”

“…A significant alteration of any of these components of the secretory process by CF factor@) is expected to lead to a demonstrable change in K' transport. This bioassay also was chosen for the following additional reasons: (1) it is an appropriate model system because it is a mammalian exocrine gland, one which is pathophysiologically altered in CF; (2) retrograde perfusion experiments have suggested that a closely related gland from the rat, the parotid, is responsive to CF humoral factor(s); (3) dispersed cell suspension of this organ has been perfected, obviating many technical problems associated with in vivo perfusion and in vitro gland slice experiments (21-23); (4) a pharmacologic description of the ion-coupled secretory response is available (23)(24)(25); (5) responses of the bioassay are readily quantitated, a necessary attribute for the rigorous demonstration and characterization of a bioactive factor.…”

Introduction of BAPTA into intact rat submandibular acini inhibits mucin secretion in response to cholinergic and β‐adrenergic agonists

“…ionophore A231 87, at non-lytic concentrations, increased the intracellular fret CaZ' concentration in rat submandibular acini bud did not trigger mucin secrction [7]. It is also not clear whether cholinergic agonists, which act via Ca"' in stimulating enzyme secretion from pancreatic acinar cells [8], increase mucin secretion from submandibular acinar cells [ 1,2,9].…”