PHOTODYNAMIC TRIGGERING OF CALCIUM OSCILLATION IN THE ISOLATED RAT PANCREATIC ACINI

1. Photodynamic agents, due to their photon-dependent selective activa tion, can selectively activate a number of physiological processes and may directly modulate signal transduction in a number of cells includ ing pancreatic acinar cells. 2. Activation of the photodynamic agent s ulphonated aluminium phthalocyanine (SALPC) triggered recurrent cytoso lic calcium ([Ca2+](i)) spiking in pancreatic acinar cells. 3. The pho todynamically triggered calcium spiking could be blocked by phosphatid ylinositol-specific phospholipase C (PI-PLC) inhibitor U73122, but not by phosphatidylcholine-specific phospholipase C inhibitor D809. 4. Re moval of extracellular Ca2+ abolished spiking, as did 2-aminoethoxydip henylborate (2-APB), an inhibitory modulator of IP3-mediated Ca2+ rele ase from intracellular stores. 5. These data suggest that SALPC photod ynamic action may permanently fix PI-PLC in an active conformation, an d this produced recurrent [Ca2+](i) spiking.