Autonomic regulation of somatostatin release: studies with primary cultures of canine fundic mucosal cells

Abstract

Using a newly developed system for culturing canine fundic mucosal cells, we examined regulation of the secretion of somatostatinlike immunoreactivity (SLI) by cholinergic and adrenergic transmitters. Enzyme-dispersed canine fundic mucosa cells were enriched in SLI content by counterflow elutriation and cultured on collagen for 42 h. Epinephrine alone, and in combination with gastrin, stimulated SLI secretion in a dose-dependent fashion. Propranolol did not alter the response to dibutyryl cAMP or gastrin but produced a parallel, rightward shift of the epinephrine dose-response curve with the dissociation constant (Ki) determined to be 14 nM by nonlinear curve fitting. Phentolamine, an alpha-adrenergic antagonist, enhanced SLI secretion in response to epinephrine, an effect reversed by the alpha 1-agonist methoxamine but not by the alpha 2-agonist clonidine. However, neither methoxamine nor clonidine alone inhibited the response to the beta-selective adrenergic agonist isoproterenol; thus, the existence of an adrenergic alpha 1-inhibitory receptor remained uncertain. Carbachol noncompetitively inhibited SLI secretion stimulated by gastrin, epinephrine, and dibutyryl cAMP. Atropine produced a parallel rightward shift of the carbachol dose-response curve (Ki = 0.4 nM). Pirenzepine also inhibited the effects of carbachol (Ki = 35 nM). Our studies suggest that SLI-containing cells in the canine fundic mucosa possess stimulatory beta-adrenergic receptors and inhibitory muscarinic receptors.