Summary
The present communication deals with the possible effect of glucagon released from the alpha-cells upon insulin secretion induced by glucose in the adjacent beta-cells. First, it has been shown that neutral red, a substance which is thought to cause glucagon release from the alpha-cells, did not modify the rate of insulin secretion induced by glucose in pieces of rat pancreatic tissue. Secondly, glucose stimulated insulin secretion under conditions where imidazole, a substance known to activate the phosphodiesterase, completely abolished the stimulant effect of exogenous glucagon upon insulin secretion. It is concluded that glucagon is not necessarily involved in the stimulation of insulin secretion by glucose, and that the effect of locally released glucagon, if any, is only to enhance the stimulant action of glucose.
Résumé
Les auteurs envisagent le rôle éventuel que joue le glucagon libéré par les cellules alpha dans la sécrétion d'insuline induite par le glucose dans les cellules beta voisines. Le rouge neutre, qui est supposé libérer le glucagon des cellules alpha, ne modifie pas la sécrétion d'insuline provoquée par le glucose dans le tissu pancréatique du rat. De plus, le glucose stimule la sécrétion d'insuline en présence d'imidazole, un activateur de la phosphodiestérase, utilisé en concentrations suffisantes pour abolir l'effet du glucagon exogène. Ces données suggèrent que le glucagon n'est pas nécessairement impliqué dans la stimulation de la sécrétion d'insuline par le glucose, et qu'un éventuel effet du glucagon libéré localement parles cellules alpha se limite à potentialiser l'action stimulatrice du glucose.
Zusammenfassung
Die Autoren untersuchten die Rolle, die das aus den α-Zellen freigesetzte Glucagon eventuell bei der durch Glucose stimulierten Insulinsekretion aus den benachbarten β-Zellen spielt. Neutralrot soll zwar Glucagon aus den α-Zellen freisetzen, führt aber zu keiner Änderung der glucosestimulierten Insulinsekretion des Rattenpankreas. Ferner stimuliert Glucose die Insulinsekretion, auch wenn man Imidazol, einen Aktivator der Phosphodiesterase in Mengen zusetzt, die ausreichen, um den Effekt von exogenem Glueagon zu unterdrücken. Auf Grund dieser Befunde kann man annehmen, daß Glueagon nicht notwendigerweise in die durch Glucose stimulierte Insulinsekretion eingreift und daß ein eventueller Effekt von lokal aus den α-Zellen freigesetztem Glucagon sich auf eine Verstärkung der Stimulationswirkung von Glucose beschränkt.
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Supported in part by a grant-in-aid from the Lilly Research Laboratories, and by the association contract Euratom-Universities of Pisa and Brussels (026-63-04 BIAC).
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Malaisse, W., Malaisse-Lagae, F. & King, S. Effects of neutral red and imidazole upon insulin secretion. Diabetologia 4, 370–374 (1968). https://doi.org/10.1007/BF01211774
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DOI: https://doi.org/10.1007/BF01211774