Modulation of intracellular Ca2+ in the parathyroid cell. Release of Ca2+ from non-mitochondrial pools by inositol trisphosphate |
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Authors: | P A Epstein M Prentki M F Attie |
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Affiliation: | Endocrine Section, Department of Medicine and Department of Biochemistry, University of Pennsylvania, 531 Johnson Pavillion, Philadelphia, PA 19104, USA |
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Abstract: | Stimuli which enhance secretion from parathyroid cells such as low extracellular Ca2+ or Mg2+ are associated with a decrease in the cytosolic Ca2+ concentration as measured by quin2. Current evidence suggests that increased production of inositol 1,4,5-triphosphate (IP3) releases Ca2+ from cellular stores thus increasing cytosolic Ca2+. We used saponin-permeabilized dispersed bovine parathyroid cells to study the effect of IP3 on intracellular Ca2+. IP3 released Ca2+ from these cells in a dose-dependent manner; half-maximal response occurred with 0.3 microM IP3 and maximal response with 1.2 microM IP3. Permeabilized cells incubated in the presence of the mitochondrial inhibitor antimycin A released a similar amount of Ca2+ suggesting that IP3 releases Ca2+ from a non-mitochondrial pool. These results suggest that IP3 regulates cytosolic Ca2+ in this system and may function as a second messenger controlling hormone secretion. |
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