Cyclic ADP-ribose and inositol 1,4,5-triphosphate mobilizes Ca2+ from distinct intracellular pools in permeabilized lacrimal acinar cells.
In permeabilized lacrimal acinar cells, cyclic ADP-ribose (cADP-ribose) and inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) release Ca2+ in a dose dependent manner from distinct thapsigargin-sensitive Ca2+ pools. Ryanodine specifically blocks the Ca2+ response to cADP-ribose, whereas heparin strongly reduces the response to Ins(1,4,5)P3 application. GTP causes a rapid Ca2+ release by a ryanodine- and heparin-insensitive mechanism and potentiates Ins(1,4,5)P3 but not cADP-ribose evoked Ca2+ release. It is estimated that cADP-ribose can release 16 mumol Ca2+/l cells, whereas Ins(1,4,5)P3 can mobilize 55 mumol Ca2+/l cells. The results suggest that cADP-ribose and Ins(1,4,5)P3 release Ca2+ from distinct internal stores and that a third Ca2+ pool exists which can selectively interact with the Ins(1,4,5)P3-sensitive Ca2+ store by a GTP-mediated process.
Gromada
J
J
Department of Medical Physiology, University of Copenhagen, Panum Institute, Denmark.
Jørgensen
T D
TD
Dissing
S
S
D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology*; D002451:Cell Compartmentation; D002463:Cell Membrane Permeability; D036563:Cyclic ADP-Ribose; D003593:Cytoplasm / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D066298:In Vitro Techniques; D007765:Lacrimal Apparatus / Q000187:drug effects*; D051381:Rats; D012433:Ryanodine / Q000494:pharmacology; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D013729:Terpenes; D036563:Cyclic ADP-Ribose; D012433:Ryanodine; D000246:Adenosine Diphosphate Ribose; D019284:Thapsigargin; D006160:Guanosine Triphosphate; D006493:Heparin; D002118:Calcium