Cytoplasmic calcium transients due to single action potentials and voltage-clamp depolarizations in mouse pancreatic B-cells.

Journal article

Changes in the cytoplasmic free calcium concentration ([Ca2+]i) in pancreatic B-cells play an important role in the regulation of insulin secretion. We have recorded [Ca2+]i transients evoked by single action potentials and voltage-clamp Ca2+ currents in isolated B-cells by the combination of dual wavelength emission spectrofluorimetry and the patch-clamp technique. A 500-1000 ms depolarization of the B-cell from -70 to -10 mV evoked a transient rise in [Ca2+]i from a resting value of approximately 100 nM to a peak concentration of 550 nM. Similar [Ca2+]i changes were associated with individual action potentials. The depolarization-induced [Ca2+]i transients were abolished by application of nifedipine, a blocker of L-type Ca2+ channels, indicating their dependence on influx of extracellular Ca2+. Following the voltage-clamp step, [Ca2+]i decayed with a time constant of approximately 2.5 s and summation of [Ca2+]i occurred whenever depolarizations were applied with an interval of less than 2 s. The importance of the Na(+)-Ca2+ exchange for B-cell [Ca2+]i maintenance was evidenced by the demonstration that basal [Ca2+]i rose to 200 nM and the magnitude of the depolarization-evoked [Ca2+]i transients was markedly increased after omission of extracellular Na+. However, the rate by which [Ca2+]i returned to basal was not affected, suggesting the existence of additional [Ca2+]i buffering processes.

Authors: Rorsman, P; Ammälä, C; Berggren, P; Bokvist, K; Larsson, O

• Publication status: Published
• Journal: EMBO journal
• Volume: 11
• Issue: 8
• Pages: 2877-2884
• Publication date: 1992-08-01
• EISSN: 1460-2075
• ISSN: 0261-4189
• Language: English
• Keywords: Membrane Potentials; Sodium-Calcium Exchanger; Indoles; Spectrometry, Fluorescence; Fluorescent Dyes; Mice; Calcium; Cytoplasm; Animals; Carrier Proteins; Sodium; Nifedipine; Membrane Proteins; Islets of Langerhans