Coupling of exocytosis to depolarization in rat pancreatic islet β-cells: effects of Ca2+, Sr2+and Ba2+-containing extracellular solutions

✍ Scribed by David W. Barnett; Stanley Misler

• Publisher: Springer
• Year: 1995
• Tongue: English
• Weight: 333 KB
• Volume: 430
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00373898

✦ Synopsis

Using rat [3-cells we present evidence that Sr 2+ and Ba 2+, like Ca 2+, support depolarization-induced increases in membrane capacitance which reflect insulin granule exocytosis. Even with identical total charge entry, Sr 2+ and Ba 2+ are 3-5 and 20-fold less effective than Ca 2+ in supporting release. While exocytosis supported by Sr2+ is graded with cation entry and complete within 250ms of depolarization, exocytosis supported by Ba 2+ begins abrupty after a threshold of charge entry and continues for many seconds. Ba2+-supported release continues in the presence of greatly enhanced cytosolic Ca 2+ buffering, arguing against release of Ca 2+ from stores as its principal action. These results suggest that Sr2+ and Ba 2+ support exocytosis largely by binding to Ca2+-dependent releaseactivating sites, though with less affinity than Ca 2+ .