Regulation of intracellular Ca2+ oscillation in AR42J cells.
Recordings of [Ca2+]i in single AR42J cells loaded with Fura 2 were used to study regulation of [Ca2+]i oscillation. Continuous stimulation with the cholecystokinin analogue, (t-butyloxycarbonyl-Tyr-(SO3)-norleucine-Gly-Trp-Nle-Asp-2-phenylethyl ester) or carbachol evoked long lasting oscillation in [Ca2+]i. Removal of CCK-JMV-180 after brief stimulation did not abruptly stop the oscillation. Rather, removal of CCK-JMV-180 resulted in time-dependent reduction in amplitude with little change in frequency of oscillation. The patterns of [Ca2+]i oscillation were affected by activation of protein kinase C and protein kinase A. However, down-regulation of protein kinase C activity did not prevent stimulation of [Ca2+]i oscillation. Hence, we conclude that an active protein kinase C pathway is not crucial for [Ca2+]i oscillation in this cell line. Variation in extracellular Ca2+ concentration (Ca2+out) was used to further characterize the oscillation. Reducing Ca2+out to approximately 10 microM resulted in a time dependent inhibition of [Ca2+]i oscillation. Subsequent step increases in Ca2+out up to 2-3 mM resulted in increased amplitude and frequency of oscillation. Further increase in Ca2+out or an increase in plasma membrane permeability to Ca2+, brought about by an increase in pHo, resulted in increased amplitude, decreased frequency, and modified shape of the [Ca2+]i spikes. These observations point to the existence of regulatory mechanisms controlling the duration of Ca2+ release and entry during [Ca2+]i oscillation.
Department of Physiology, University of Texas Southwestern Medical Center, Dallas 75235.
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Zhao
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Loessberg
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Muallem
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D002460:Cell Line; D007700:Kinetics; D009991:Oscillometry; D010179:Pancreas; D012844:Sincalide / Q000031:analogs & derivatives / Q000494:pharmacology; D013050:Spectrometry, Fluorescence / Q000379:methods; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
C058451:JMV 180; D012844:Sincalide; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine