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Ca2+ mobilization from intracellular stores constitutes an important mechanism for generating cytoplasmic Ca2+ signals. Inositol trisphosphate (InsP3) and ryanodine receptors are the two families of intracellular Ca2+ release channels that have been identified, which may be regulated by separate intracellular messengers, InsP3, and cyclic adenosine 5'-diphosphate ribose, respectively. A third molecule, nicotinic acid adenine dinucleotide phosphate (NAADP), has recently been recognized as a potent Ca2+ releasing agent in sea urchin eggs and microsomes. We now report that non-releasing concentrations of NAADP fully and irreversibly inactivate the NAADP-sensitive Ca2+ release mechanism. This phenomenon occurred both in intact sea urchin eggs and in homogenates and is not shared by either InsP3 or cyclic adenosine 5'-diphosphate ribose. The novel properties of this Ca2+ release mechanism, giving a one-shot Ca2+ release, may be suited to irreversible cellular events.

Original publication




Journal article


The Journal of biological chemistry

Publication Date





11599 - 11602


Department of Pharmacology, University of Oxford, United Kingdom.


Ovum, Animals, Sea Urchins, Calcium, NADP, Female