Studies on the Cellular Interrelationship in the Islets of Langerhans (2):Phygiologic Role of Somatostatin and Glucagon in lnsolin Rolease

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The present investigation was undertaken to clarify interrelationship among A, B and D cells in the islets of Langerhans with special reference to insulin release in vivo and in vitro. Ten islets isolated from Wistar male rats with collagenase method were preincubated in Krebs-Henseleit bicarbonate buffer (pH 7.4) containing 3.3 mM glucose in the gas phase of 95%O2-5%CO2 at 37° for 20 minutes, being followed by the incubation in 0.7 ml of Krebs-Henseleit bicarbonate buffer containing various concentration of glucose and anti-somatostatin serum (ASS), antiglucagon serum (AGS) or normal rabbit serum (NRS) for 60 minutes under the similar conditions to those in the preincubation. Besides, blood was sampled before and 30 minutes after the administration of ASS or NRS under pentobarbital anesthesia in rats. (1) The antiserum used in the incubation studies did not cross-react to the other peptide hormones presumably or definitely existing in the islets than its antigen peptide. (2) Insulin release from ASS-treated islets was enhanced in the presence of 3.3 and 8.3mM glucose compared with that from NRS-treated islets, whereas in the presence of 16.7mM glucose there was no difference in insulin release between both treatments. (3) On the contrary, glucagon release from AGS-treated islets was suppressed in 3.3 and 83mM glucose in contrast with that from NRS-treated islets, while in 16.7 mM glucose the suppression disappeared. (4) Plasma insulin and glucagon levels were elevated in rats 30 minutes after administration compared with those prior to the injection, while plasma glucose revealed no significant changes. On the other hand, plasma insulin and glucagon levels were not elevated after NRS treatment. It is, therefore, suggested that somatostatin and glucagon play an important role in the regulation of insulin release in the physiologic range of glucose concentration and that somatostatin might be involved in insulin release directly as well as through glucagon suppression.

Studies on the Cellular Interrelationship in the Islets of Langerhans (2):Phygiologic Role of Somatostatin and Glucagon in lnsolin Rolease

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