Control of cytoplasmic calcium with photolabile tetracarboxylate 2-nitrobenzhydrol chelators.
This paper introduces nitr-2, a new Ca2+ chelator designed to release Ca2+ upon illumination with near UV (300-400 nm) light. Before illumination nitr-2 has Ca2+ dissociation constants of 160 and 630 nM in 0.1 and 0.3 M ionic strength respectively; after photoconversion to a nitrosobenzophenone the values shift to 7 and 18 microM, high enough to liberate substantial amounts of Ca2+ under intracellular conditions. The speed of release is limited by a dark reaction with rate constant 5 s-1. Aplysia central neurons injected with nitr-2 and exposed to UV light exhibit two separate Ca2+-dependent membrane currents: one carried by potassium ions and one a nonspecific cation current. A quantitative estimate of the spatial distribution of intracellular [Ca2+] changes in large cells filled with a high concentration of nitr-2 and exposed to an intense UV flash is offered.
D000818:Animals; D001048:Aplysia; D002118:Calcium / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology*; D003593:Cytoplasm / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000502:physiology; D010782:Photolysis
D002614:Chelating Agents; C051166:nitr 2; D004533:Egtazic Acid; D002118:Calcium