Dynamics of insulin release by perfused edible dormouse (Glis glis) pancreas

Abstract

Summary.In order to characterize seasonal variations of beta cell function in the edible dormouse (Glis glis), the dynamics of insulin release were examined during perfusion of the isolated pancreas. The B cells exhibited biphasic insulin secretion; however, the dynamic response differed from that of the rat in that there was a steady-state second release phase. Glucose-induced insulin release changed according to the seasons. With 16.8 mmol/1 glucose, the average insulin release of the late phase was 30.8 + 12.6 ng/min in winter, 7.4 + 3.2 ng/min in spring, 13.1 + 3 ng/min in summer and 23.3 + 4.4 ng/min in autumn. The glucose-induced insulin release, expressed as percent of the insulin content of the pancreas, varied according to the season: it represented 2.23 + 0.31% in winter, 1.28 + 0.10% in spring, 1.56 + 0.15 in summer and 2.6 + 0.11 in autumn. It is suggested that in spring and summer, the edible dormouse B cell secretion mechanism is less sensitive to glucose than in the other seasons.Key words: Edible dormouse (Glis glis), hibernating mammal, dynamics of insulin release, insulin secretion, glucose-stimulated insulin secretion, perfused pancreas, B cell, seasonal variations.Glucose tolerance tests performed in the edible dormouse have shown seasonal variations in the plasma insulin response, associated with glucose tolerance changes [1]. In autumn and in winter, the glucoseinduced plasma insulin concentrations are increased and insulin regulates the high peripheral consumption of this hexose; at the beginning of spring, it decreases and glucose tolerance is impaired. In June plasma insulin levels are low and poor glucose tolerance persists.Glucose tolerance tests give useful information about glucose effects on B cell function. In vivo tests are limited however, in that insulin secretagogues could act through secondary effects rather than through a direct action on the B cell [2]. In order to circumvent this problem and to discover if seasonal variations of plasma insulin levels after glucose loading are due to variations of insulin secretion, we have studied insulin secretion of the perfused pancreas of the edible dormouse and compared values with those found in the rat. Material and Methods

Clinical Biochemistry and Hematology

“…GLUCOSE Glucose-induced insulin release was studied in the perfused pancreas of the edible dormouse (Glis glis) and demonstrated seasonal variation in this species. Exposure of the dormouse to 302 mg/dl glucose caused highest insulin release in the fall and winter and decreased glucose sensitivity in the spring and summer (Castex and Sutter, 1981).…”