A probe for intracellular concentrations of drugs: delayed fluorescence from acridine orange.
The aim of this work is to develop fluorescent probes that will indicate effective concentrations of therapeutic agents, or endogenous protectors, at important cellular sites. Acridine orange associates with nucleic acids and emits a 'delayed' fluorescence signal. This signal is quenched by oxidants such as oxygen, nitroaryl radiosensitizers, adriamycin and mitomycin-c, and reductants such as thiols, ascorbate and other radioprotectors. The quenching of the acridine orange delayed fluorescence reflects the effective concentration of these therapeutically-important oxidants and reductants near DNA. The relative concentration of basic radiosensitizers such as pimonidazole (Ro 03-8799) near the DNA is greater than that of misonidazole. Thiols quench the delayed fluorescence signal according to the degree of ionization of the thiol function; this may model the reactivity of thiols with guanine radical sites in DNA. Ascorbate and aminopyrine do not quench the delayed fluorescence from cells stained with acridine orange as these compounds are taken up by cells very inefficiently.
Wardman
P
P
Cancer Research Campaign, Mount Vernon Hospital, Northwood, Middx., U.K.
Dennis
M F
MF
White
J
J
D000165:Acridine Orange; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002460:Cell Line; D004247:DNA / Q000187:drug effects* / Q000528:radiation effects; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D010084:Oxidation-Reduction; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D013997:Time Factors
D000970:Antineoplastic Agents; D005456:Fluorescent Dyes; D011838:Radiation-Sensitizing Agents; D013438:Sulfhydryl Compounds; D004247:DNA; D000165:Acridine Orange