A novel aspect of photodynamic action: induction of recurrent spikes in cytosolic calcium concentration.
Effects of photodynamic action of gadolinium porphyrin-like macrocycle B (PLMGdB) on cytosolic Ca2+ concentration, [Ca2+]c, was investigated in isolated rat pancreatic acini. The PLMGdB alone or light alone (2 min) had no effect on [Ca2+]c. Cell-bound PLMGdB upon brief (0.5-2.0 min) light activation triggered recurrent spikes in [Ca2+]c. At lower PLMGdB concentration (100 nM) the spikes continued during the whole period of monitoring [Ca2+]c. At a higher concentration of 500 nM, the spikes continued for the first 40 min, followed by a gradual increase in basal [Ca2+]c upon which smaller spikes were superimposed. At 1 microM, the spikes continued for the first 20 min, after that spiking gradually degenerated into a plateau phase. In many aspects, photodynamically triggered spikes resembled spikes generated by physiological concentrations of cholecystokinin. The spikes triggered by photodynamic action were likely to be the result of the ignition of a physiological "chain reaction", because functional inositol-1,4,5-trisphosphate (IP3) receptors were required for spiking to occur. Two-aminoethoxydiphenylborate, an inhibitory modulator of IP3-triggered Ca2+ release from intracellular stores, effectively inhibited photodynamically generated spikes. Therefore photodynamic action appears to be able to permanently transfix a physiological process, leading to long-lasting pharmacological or therapeutic effects.
Cui
Z J
ZJ
Beijing Agricultural University Faculty of Biological Sciences, P.R. China. bauic@public.bta.net.cn
Habara
Y
Y
Wang
D Y
DY
Kanno
T
T
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D003600:Cytosol / Q000378:metabolism; D004594:Electrophysiology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008297:Male; D008665:Metalloporphyrins / Q000494:pharmacology*; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008665:Metalloporphyrins; D017319:Photosensitizing Agents; D018160:Receptors, Cytoplasmic and Nuclear; D002118:Calcium