Shear stress-induced [Ca2+]i transients and oscillations in mouse fibroblasts are mediated by endogenously released ATP.
The effects of ATP, U-73122, apyrase, and saline shear stress on [Ca2+]i homeostasis were studied in fura-2 loaded, mouse fibroblast cells (L929), both in suspension and plated on glass. Release of internal Ca2+ was induced by ATP, via a receptor identified pharmacologically as a P2U type. In single cells, low concentrations of ATP evoked [Ca2+]i oscillations. These events were blocked by the putative phospholipase C inhibitor, U-73122 (but not by the inactive analog U-73343) and by the ATP/ADPase, apyrase. In addition, both these agents reduced the [Ca2+]i of unstimulated cells, especially after stirring, and blocked spontaneously occurring [Ca2+]i oscillations, which suggested an already activated state of the ATP receptor, independent from exogenous stimulations. Moreover, it was found that stirring of the cells was correlated with a steady accumulation of inositol phosphates, also blockable by apyrase, and that [Ca2+]i mobilization could be induced by puffs of saline in single cells. The transition to a Ca(2+)-free environment also provoked [Ca2+]i oscillations, most likely via the increase in ATP4- concentration. This evidence suggests that endogenous ATP is released from L fibroblasts in response to fluid shear stress, and this results in an autocrine, tonic up-regulation of the phosphoinositide signaling system and an ensuing alteration in Ca2+ homeostasis. Up until now, such a response to shear stress was believed to be unique to endothelial cells.
Grierson
J P
JP
Department of Pharmacology, University of Milano, CNR, Italy.
Meldolesi
J
J
D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D001081:Apyrase / Q000494:pharmacology; D001696:Biomechanical Phenomena; D002118:Calcium / Q000378:metabolism*; D004963:Estrenes / Q000494:pharmacology; D006706:Homeostasis; D006868:Hydrolysis; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007739:L Cells; D051379:Mice; D011760:Pyrrolidinones / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology
D004963:Estrenes; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D012965:Sodium Chloride; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D001081:Apyrase; D002118:Calcium