Evidence for the possible involvement of the P2Y6 receptor in Ca2+ mobilization and insulin secretion in mouse pancreatic islets

• Published in: Purinergic signalling 2008-12, Vol.4 (4), p.365-375, Article 365
• Main Authors: Ohtani, Masahiro, Suzuki, Jun-ichiro, Jacobson, Kenneth A., Oka, Takami
• Format: Article
• Language: English
• Subjects: Biomedical and Life Sciences; Biomedicine; Cancer Research; Human Physiology; Neurosciences; Original; Original Article; Pharmacology/Toxicology
• ISSN: 1573-9538; 1573-9546
• DOI: 10.1007/s11302-008-9122-2

Subtypes of purinergic receptors involved in modulation of cytoplasmic calcium ion concentration ([Ca 2+ ] i ) and insulin release in mouse pancreatic β-cells were examined in two systems, pancreatic islets in primary culture and beta-TC6 insulinoma cells. Both systems exhibited some physiological responses such as acetylcholine-stimulated [Ca 2+ ] i rise via cytoplasmic Ca 2+ mobilization. Addition of ATP, ADP, and 2-MeSADP (each 100 µM) transiently increased [Ca 2+ ] i in single islets cultured in the presence of 5.5 mM (normal) glucose. The potent P2Y 1 receptor agonist 2-MeSADP reduced insulin secretion significantly in islets cultured in the presence of high glucose (16.7 mM), whereas a slight stimulation occurred at 5.5 mM glucose. The selective P2Y 6 receptor agonist UDP (200 µM) transiently increased [Ca 2+ ] i and reduced insulin secretion at high glucose, whereas the P2Y 2/4 receptor agonist UTP and adenosine receptor agonist NECA were inactive. [Ca 2+ ] i transients induced by 2-MeSADP and UDP were antagonized by suramin (100 µM), U73122 (2 µM, PLC inhibitor), and 2-APB (10 or 30 µM, IP 3 receptor antagonist), but neither by staurosporine (1 µM, PKC inhibitor) nor depletion of extracellular Ca 2+ . The effect of 2-MeSADP on [Ca 2+ ] i was also significantly inhibited by MRS2500, a P2Y 1 receptor antagonist. These results suggested that P2Y 1 and P2Y 6 receptor subtypes are involved in Ca 2+ mobilization from intracellular stores and insulin release in mouse islets. In beta-TC6 cells, ATP, ADP, 2-MeSADP, and UDP transiently elevated [Ca 2+ ] i and slightly decreased insulin secretion at normal glucose, while UTP and NECA were inactive. RT-PCR analysis detected mRNAs of P2Y 1 and P2Y 6 , but not P2Y 2 and P2Y 4 receptors.