Abstract
We have characterised sites of photodamage catalysed by the cationic photosensitiser tetrabromorhodamine 123, using P388 murine leukaemia cells and a subline (P388/ADR) which has a multidrug resistance phenotype and hyperexpresses mdr1 mRNA for P-glycoprotein. Fluorescence emission spectra were consistent with sensitiser localisation in hydrophobic regions of the P388 cell, and in more aqueous loci in P388/ADR. Subsequent irradiation resulted in photodamage to the P388 cells, resulting in loss of viability. In contrast, P388/ADR cells were unaffected except for an irreversible inhibition of P-glycoprotein, leading to enhanced accumulation of daunorubicin and rhodamine 123 and a corresponding increase in daunorubicin cytotoxicity. These results are consistent with the premise that substrates for P-glycoprotein are confined to membrane loci associated with the transporter, and indicate a very limited migration of cytotoxic photo-products in a cellular environment.
Highlights
The phenomenon of multidrug resistance (MDR) has been well characterised (Germann et al.. 1993: Gottesman and Pastan, 1993; Tew et al, 1993)
MDR is associated with a membrane-bound multidrug transporter: a glycoprotein (P-glycoprotein, P-gp) which serves as an ATPdependent outward transport system
The P388,ADR cell line used in these studies exhibits the characteristics of this MDR phenotype: a membrane glycoprotein with a molecular weight of approximately 180000 (Kessel and Corbett, 1985) and a broad spectrum of drug resistance associated with enhanced energy-dependent outward transport of anthracyclines (Johnson et al, 1982) which is antagonised by verapamil and related agents (Kessel and Wilberding, 1985)
Summary
The phenomenon of multidrug resistance (MDR) has been well characterised (Germann et al.. 1993: Gottesman and Pastan, 1993; Tew et al, 1993). P388 and P388 ADR cells were incubated with 5 lim TBR for 30 min at 37'C. resuspended in buffered salts medium at l0'C and irradiated using a 600 W QH lamp with transmission limited to 500 ± 20 nm bv an interference filter. Steady-state conditions were obtained by incubation of control and irradiated cells in buffered salts medium at 37°C for 10 min with 0.1 LM [14C)cycloleucine or for 30 min with 0.3 Am ['4C]daunorubicin.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
