Insulin and glucagon release from monolayer cell cultures of pancreas from newborn rats.

Abstract

Abstract. Monolayer culture of pancreatic cells from newborn rats has been shown to yield ultrastructurally normal endocrine cells, virtual absence of differentiated exocrine cells, and the maintenance of the capacity to synthesize immuno‐reactive insulin (IRI) and glucagon (ERG). Such a preparation has potential advantages for the study of mechanisms of hormone synthesis and release. Therefore, a survey of factors influencing hormone content and release from cultured cells was undertaken. The following general features were demonstrated: (1) highly reproducible responses within a given preparation of cells despite (2) some variations of absolute hormone content and release between preparations, (3) suitability for preparing sufficient quantities of cells to permit the simultaneous comparison of several factors within a given preparation, and (4) persistence of physiological responses to known modulators of IRI and IRG release. Thus, IRI release was stimulated in concentration‐related fashion by glucose. Amino acids, tolbutamide and glucagon augmented release, and 2‐deoxy‐D‐glucose, mannoheptulose and diazoxide inhibited glucose‐induced release. Epinephrine inhibited glucose‐induced IRI release through stimulation of an α‐adrenergic receptor mechanism, and the presence of probable β‐receptor stimulation of release was also demonstrated. Agents affecting the microtubular‐microfilamentous system exerted effecte similar to those demonstrated in other preparations. Ouabain, as well as the absence or augmented potassium in the medium increased IRI release in the presence of non‐stimulatory 2.75 mM glucose, whereas absence of calcium inhibited the response to 11 mM glucose without affecting baseline, non‐stimulated release. IRG release was shown to be inversely related to the glucose concentration in the medium. It was stimulated by epinephrine, arginine, alanine, lactate and pyruvate, and inhibited by β‐hydroxybutyrate. Diazoxide alone had no effect on IRG release. The monolayer culture employed in these studies provides a convenient, reproducible system for the further study of adult‐type IRI and IRG secretory behaviour. In addition to acute or short‐term regulation it may be especially suited for the study of long‐term modulating effects during the culture period.