Endocrine Abstracts

Paradoxical effects of GABA on glucose-stimulated insulin secretion from isolated islets in rat

Farzaneh Faraji Shahrivar¹, Asghar Ghasemi¹, Fereshteh Motamedi² & Saleh Zahedi Asl¹

¹Endocrine Physiology Laboratory, Research Institute for Endocrine Sciences, Endocrine Research Center, Shahid Beheshti University (M.C.), Tehran, Islamic Republic of Iran; ²Neurosciences Research Center, Shahid Beheshti University (M.C.), Tehran, Islamic Republic of Iran.

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Introduction: The islets of pancreas contain relatively high levels of Gamma-amino butyric acid (GABA). This study was designed to determine the role of the GABA and GABA_B receptor on glucose-stimulated insulin secretion of isolated islets in rats.

Materials and methods: The Collagenase digestion technique was used to isolate the islets from male Wistar rats and insulin secretion was assessed in islets exposed to glucose (8.3, 16.7 mM) in presence and absence of GABA (25, 50, and 100 μM), a GABA_B agonist, baclofen (10, 20, and 50 μM) and GABA_B antagonist, saclofen (50 and 100 μM); islets were incubated in Krebs–Ringer solution at 37°C in the presence of different drugs. Following this insulin secretion was measured by the ELISA method and reported as mean±S.E.M. μU/islet per minute. One-way analysis of variance was used for comparing means between groups.

Results: When 50 μM GABA was added 45 min before glucose, insulin secretion was found to be increased during 60 min incubation time; however adding GABA and glucose simultaneously caused a significant decrease in insulin secretion. Baclofen had no significant effect on glucose-induced insulin secretion, whereas 100 μM Saclofen significantly increased glucose (16.7 mM) stimulated insulin secretion (91±8.8 vs 67.7±2.58 μU/islet per 60 min, P<0.05).

Conclusion: GABA could have both stimulatory and inhibitory effects on glucose-stimulated insulin secretion, depending on the time of exposure.

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Endocrine Abstracts (2009) 20 P348