Ca2+ oscillations induced by hormonal stimulation of individual fura-2-loaded hepatocytes.
Isolated rat hepatocytes were loaded with the Ca2+ indicator fura-2 to measure cytosolic free Ca2+ concentrations ([Ca2+]i) in individual cells by digital ratio imaging microscopy. Stimulation with 0.1 nM vasopressin, 0.5 microM phenylephrine, or 0.5 microM ATP caused repetitive spikes of high [Ca2+]i in a high percentage of cells, in agreement with Woods et al. (Woods, N. M., Cuthbertson, K. S. R., and Cobbold, P. H. (1986) Nature 319, 600-602), but unlike the results of Monck et al. (Monck, J. R., Reynolds, E. E., Thomas, A. P., and Williamson, J. R. (1988) J. Biol. Chem. 263, 4569-4575). Reduction in extracellular [Ca2+] decreased the frequency but not the amplitude of the spikes, suggesting that the spikes result from dumping of intracellular stores and that the entry of extracellular Ca2+ affects only the rate of replenishment of those stores. Membrane depolarization failed to elevate [Ca2+]i and had an effect similar to removal of extracellular Ca2+ in decreasing the frequency of agonist-evoked [Ca2+]i oscillations or inhibiting them altogether, arguing against any significant role for voltage-operated Ca2+ channels.
Kawanishi
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Department of Physiology-Anatomy, University of California, Berkeley 94720.
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Harootunian
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Smith
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Tsien
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D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001572:Benzofurans; D002118:Calcium / Q000502:physiology*; D003600:Cytosol / Q000502:physiology; D005110:Extracellular Space / Q000502:physiology; D005456:Fluorescent Dyes; D016257:Fura-2; D006096:Gramicidin / Q000494:pharmacology; D006868:Hydrolysis; D008099:Liver / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D010656:Phenylephrine / Q000494:pharmacology; D011188:Potassium / Q000502:physiology; D051381:Rats; D014667:Vasopressins / Q000494:pharmacology
D001572:Benzofurans; D005456:Fluorescent Dyes; D014667:Vasopressins; D006096:Gramicidin; D010656:Phenylephrine; D000255:Adenosine Triphosphate; D011188:Potassium; D002118:Calcium; D016257:Fura-2