Dual effects of cyclic ADP-ribose on sarcoplasmic reticulum Ca2+ release and storage in cardiac myocytes isolated from guinea-pig and rat ventricle.
The actions of cyclic ADP-ribose (cADPR), a regulator of Ca2+-induced Ca2+ release (CICR), were investigated on Ca2+ release and sarcoplasmic reticulum (SR) Ca2+ loading in cardiac myocytes at physiological temperature. In guinea-pig ventricular cells, cADPR, applied via patch pipette or from photorelease of its caged derivative, increased contraction amplitude and whole-cell Ca2+ transients, without affecting SR Ca2+ load (measured in response to rapid caffeine application). Under voltage-clamp conditions, photorelease of caged cADPR enhanced Ca2+ transient magnitude without affecting the peak amplitude of L-type Ca2+ current or its rate of decay, indicative of an increase in CICR gain. In rat permeabilised ventricular myocytes, rapid application of cADPR increased Ca2+ spark frequency within 30 s, and this effect was maintained over a 10 min exposure. Enhancement of spark frequency was not associated with changes in SR Ca2+ load at 30 s and 3 min of exposure to cADPR; however, prolonged exposure (10 min) was associated with an increased SR Ca2+ load (32+/-7%). The observations are consistent with dual actions of cADPR: a rapid effect on CICR that does not depend on an increased SR Ca2+ load, and an additional slower effect that is associated with enhanced SR Ca2+ levels.
Macgregor
Andrew T
AT
Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, United Kingdom.
Rakovic
Stevan
S
Galione
Antony
A
Terrar
Derek A
DA
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D036563:Cyclic ADP-Ribose / Q000031:analogs & derivatives* / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism
C092958:caged cyclic ADP-ribose; D036563:Cyclic ADP-Ribose; D002118:Calcium