title: Nicotinate-adenine dinucleotide phosphate-induced Ca(2+)-release does not behave as a Ca(2+)-induced Ca(2+)-release system.
abstract: We investigated the dependence of nicotinate-adenine dinucleotide phosphate (NAADP)-induced Ca2+ release from intracellular stores of sea urchin egg homogenates, upon extravesicular Ca2+. In contrast to the Ca2+ release induced inositol 1',4',5'-triphosphate (IP3) or cyclic ADP-ribose (cADPR), the Ca2+ release induced by NAADP was completely independent of the free extravesicular Ca2+ over a wide range of concentrations (0-0.1 mM). The Ca2+ release triggered by either cADPR or IP3 was biphasically modulated by extravesicular Ca2+, and the Ca2+ release by these agents was abolished when the extravesicular Ca2+ was removed by chelation with 2 mM EGTA. On the other hand, NAADP-triggered Ca2+ release was not influenced by EGTA. These data indicate that while both cADPR and IP3 systems behave as functional Ca(2+)-induced Ca2+ release mechanisms, NAADP activates a Ca2+ release mechanism which is independent of the presence of extravesicular Ca2+. Therefore, the NAADP-sensitive Ca2+ release mechanisms may have a unique regulatory impact upon intracellular Ca2+ homoeostasis.
authors.affiliation: Department of Physiology, Biophysics and Internal Medicine, Mayo Clinic and Foundation, Rochester MN 55905, USA.
authors.forename: E N
authors.initials: EN
authors.lastname: Chini
authors.forename: T P
authors.initials: TP
authors.lastname: Dousa
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D036563:Cyclic ADP-Ribose; D004533:Egtazic Acid / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D007700:Kinetics; D009249:NADP / Q000031:analogs & derivatives* / Q000494:pharmacology; D010063:Ovum / Q000187:drug effects / Q000378:metabolism*; D012617:Sea Urchins; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
chemical_list: D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D013729:Terpenes; D036563:Cyclic ADP-Ribose; C015541:thionicotinamide adenine dinucleotide phosphate; D000246:Adenosine Diphosphate Ribose; D004533:Egtazic Acid; D009249:NADP; C024376:NAADP; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D002118:Calcium