Exocytotic properties of human pancreatic beta-cells.

Journal article

Pancreatic beta-cells secrete insulin in response to elevated blood glucose via Ca(2+)-dependent fusion of secretory granules with the plasma membrane (regulated exocytosis). While exocytosis has been extensively investigated in rodent beta-cells, studies on human beta-cells are scarce. We have characterized the exocytotic properties of human beta-cells by insulin release measurements, carbon fiber amperometry, and capacitance measurements using the patch-clamp technique. Voltage-clamp depolarizations evoked capacitance increases in single beta-cells in a time- and voltage-dependent manner. The capacitance responses as well as insulin release from intact islets were strongly amplified by elevation of intracellular cAMP levels. Exocytosis was more dependent on Ca(2+) influx through P/Q-type than L-type Ca(2+) channels, reflecting the relative contribution of these channels to the total Ca(2+) current. Exocytosis (as monitored by capacitance or amperometric measurements) decreased during repetitive stimulation as a result of inactivation of Ca(2+) channels as well as depletion of a readily releasable pool of granules. These results reveal both similarities and differences between human and rodent beta-cells.

Authors: Braun, M; Ramracheya, R; Johnson, P; Rorsman, P

• Publication status: Published
• Journal: Annals of the New York Academy of Sciences
• Volume: 1152
• Issue: 1
• Pages: 187-193
• Publication date: 2009-01-01
• DOI: 10.1111/j.1749-6632.2008.03992.x
• EISSN: 1749-6632
• ISSN: 0077-8923
• Language: English
• Keywords: Patch-Clamp Techniques; Insulin; Exocytosis; Cyclic AMP; Humans; Calcium Channels; Electrophysiology; Cells, Cultured; Insulin-Secreting Cells