Inositol 1,4,5-trisphosphate- and ryanodine-sensitive Ca2+ release channel-dependent Ca2+ signalling in rat portal vein myocytes.
Ca2+ signalling events were analyzed in single myocytes from rat portal vein by using a laser confocal microscope combined with the patch-clamp technique. Increase in inositol 1,4,5-trisphosphate (InsP3) concentration was obtained by photorelease from a caged precursor or intracellular dialysis of 3F-InsP3. Low InsP3 concentrations activated either small elevations of [Ca2+]i or localized Ca2+ transients whereas high InsP3 concentrations activated either homogeneous Ca2+ responses or propagated Ca2+ waves. The InsP3-evoked localized Ca2+ transients had spatio-temporal properties characteristic of Ca2+ sparks. In addition, compounds that blocked Ca2+ sparks and Ca2+ responses activated by Ca2+ jumps reduced the global InsP3-activated Ca2+ responses and suppressed the Ca2+ transients. In contrast, Ca2+ responses evoked by flash-photolytic Ca2+ jumps or caffeine were not affected by heparin (an InsP3 receptor antagonist). These results suggest that the absence of elementary Ca2+ events evoked by InsP3 may be related to the lack of clustered InsP3 receptor units in these cells, as confirmed by immunocytochemistry. Cooperativity between InsP3- and ryanodine-sensitive Ca2+ channels may represent a novel mechanism to amplify Ca2+ release from the same intracellular store and give rise to propagated Ca2+ waves.
Laboratoire de Physiologie Cellulaire et Pharmacologie Moléculaire, CNRS ESA 5017, Université de Bordeaux II, France.
F X
FX
Boittin
F
F
Coussin
N
N
Macrez
C
C
Mironneau
J
J
Mironneau
D000085:Acetates / Q000528:radiation effects; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D002478:Cells, Cultured; D005029:Ethylenediamines / Q000528:radiation effects; D015544:Inositol 1,4,5-Trisphosphate / Q000031:analogs & derivatives / Q000494:pharmacology* / Q000528:radiation effects; D053496:Inositol 1,4,5-Trisphosphate Receptors; D015640:Ion Channel Gating / Q000187:drug effects; D008845:Microinjections; D018613:Microscopy, Confocal; D018408:Patch-Clamp Techniques; D010782:Photolysis; D011169:Portal Vein / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects* / Q000378:metabolism; D012433:Ryanodine / Q000494:pharmacology*; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology
D000085:Acetates; D015220:Calcium Channels; D005029:Ethylenediamines; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D019837:Ryanodine Receptor Calcium Release Channel; C061868:inositol 1,4,5-trisphosphate 1-(2-nitrophenyl)ethyl ester; D012433:Ryanodine; C057014:DM-nitrophen; D015544:Inositol 1,4,5-Trisphosphate