|
|
||||||||
AJP - Cell Physiology, Vol 262, Issue 3 C656-C663, Copyright © 1992 by American Physiological Society
ARTICLES |
J. K. Foskett and D. Wong
Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada.
Previous studies have demonstrated in single rat parotid acinar cells that the microsomal Ca(2+)-ATPase inhibitor thapsigargin mobilizes Ca2+ specifically from the inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ store, activates plasma membrane Ca2+ permeability, and induces intracellular Ca2+ concentration ([Ca2+]i) oscillations that are quite similar to those activated by carbachol. Nevertheless, the IP3-sensitive Ca2+ store remains continuously depleted during thapsigargin-induced oscillations, indicating that this pool is not involved in the oscillation mechanism. To determine the specificity of thapsigargin's effects, in the present study we have examined the effects on [Ca2+]i in single rat parotid acinar cells of two other microsomal Ca(2+)-ATPase inhibitors, cyclopiazonic acid (CPA) and 2,5-di-tert-butyl-1,4-benzohydroquinone (BHQ), and compared them with the effects of thapsigargin in the same cells. Our results demonstrate that thapsigargin, CPA, and BHQ all similarly deplete the IP3-sensitive Ca2+ store specifically, activate plasma membrane Ca2+ influx, and induce [Ca2+]i oscillations, strongly suggesting that these agents have a specific inhibitory action on microsomal Ca(2+)-ATPase activity. BHQ, in addition, inhibits plasma membrane Ca2+ influx. The data lend strong support to a model in which the state of Ca2+ filling of the IP3-sensitive store regulates plasma membrane Ca2+ influx. These results suggest either that a Ca2+ pump is involved which is insensitive to structurally dissimilar inhibitors or that a Ca2+ pump is not involved in refilling of the Ca2+ pool involved in [Ca2+]i oscillations in these cells.
This article has been cited by other articles:
![]() |
M. R. Fowler, G. J. Cooper, and M. Hunter Regulation and identity of intracellular calcium stores involved in membrane cross talk in the early distal tubule of the frog kidney Am J Physiol Renal Physiol, June 1, 2004; 286(6): F1219 - F1225. [Abstract] [Full Text] [PDF] |
||||
![]() |
F. Plenge-Tellechea, F. Soler, and F. Fernandez-Belda On the Inhibition Mechanism of Sarcoplasmic or Endoplasmic Reticulum Ca2+-ATPases by Cyclopiazonic Acid J. Biol. Chem., January 31, 1997; 272(5): 2794 - 2800. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. J. Wolf, J. Wang, J. Turk, and R. W. Gross Depletion of Intracellular Calcium Stores Activates Smooth Muscle Cell Calcium-independent Phospholipase A2. A NOVEL MECHANISM UNDERLYING ARACHIDONIC ACID MOBILIZATION J. Biol. Chem., January 17, 1997; 272(3): 1522 - 1526. [Abstract] [Full Text] [PDF] |
||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |