Rhodamine resistance

Post-curing and chemical modification improves chemical and solvent resistance (20). Paraformaldehyde and acetylene diurea are added to a hot borax solution. Toluenesulfonamide (p and o), a few drops of phosphorous acid. Brilliant Yellow 6G [2429-76-7] Rhodamine E3B, and Rhodamine 6GDN [989-38-8] are added. After heating, the mass is cured in an oven at 150°C. The resulting cured resin is thermoset but can be ground to fine particle sizes. 

A polyester-type fluorescent resin matrix (22) is made by heating trimellitic anhydride, propylene glycol, and phthaUc anhydride with catalytic amounts of sulfuric acid. Addition of Rhodamine BDC gives a bright bluish red fluorescent pigment soluble in DME and methanol. It has a softening point of 118°C. Exceptional heat resistance and color brilliance are claimed for products of this type, which are useful for coloring plastics. 

Loo, T.W. and Clarke, D.M. (2002) Location of the rhodamine-binding site in the human multidrug resistance P-glycoprotein. Journal of Biological Chemistry, 111, 44332 14338. 

Budworth J, Davis R, Malkhandi J, Gant TW, Ferry DR, Gescher A (1996) Comparison of staurosporine and four analogues their effects on growth, rhodamine 123 retention and binding to P-glycoprotein in multidrug-resistant MCF-7/Adr cells. Br J Cancer 73 1063-1068... 

Recent studies on multidrug reversal in mouse lymphoma and MDR/COLO 320 cells have shown that phenothiazine derivatives, namely perphenazine (2) and prochlorperazine dimaleate (4), effectively inhibited rhodamine efflux [171]. Other phenothiazine derivatives such as promethazine (1), ox-omemazine (20), methotrimeprazine maleate (18), triflupromazine (11), and trimeprazine (17) differently modulated intracellular rhodamine accumulation in these resistant cells. The effect of some substitution in the phenothiazine ring was studied in mouse lymphoma cells expressing P-gp [172], The 3,7,8-trihydroxy- and 7,8-dihydroxychlorpromazine derivatives were effective P-gp inhibitors, whereas 7,8-diacetoxy-, 7,8-dimethoxy-, 7-semicarbazone-, and 5-oxo-chlorpromazine derivatives exerted only a moderate effect. 

In addition to proflavin and rhodamine, the photobleaching-resistant Cy3 and Cy5 fluorophores are also frequently used in single-molecule experiments and have been incorporated in the form of hydrazide derivatives into tRNAs via D residues (Pan et al., 2009) (Fig. 4.2). However, quantitative uptake of these hydrazide dyes requires modification of three reaction parameters higher concentrations of the hydrazide dyes (40 mM) than that required for proflavin or rhodamine (22 mM), pH 3.7 rather than pH 3.0, and 2 h reaction time instead of 45—90 min. The requirement of higher concentration is to promote formation of hydrazide adduct, while the slighdy elevated pH prevents hydrolysis of the adduct, which is acid labile. Thus, while the labeling method can be adapted to incorporate new fluorophores besides proflavin and rhodamine, it is prudent to systematically evaluate for the fluorophores under consideration for coupling efficiency as a function of dye concentration, pH, and reaction time. 

Altenberg GA, Vanoye CG, Horton JK, et al. Unidirectional fluxes of rhodamine 123 in multidrug-resistant cells evidence against direct drug extrusion from the plasma membrane. Proc Natl Acad Sci USA 1994 91 ( I I ) 4654 4657. 

Eytan GD, Regev R, Oren G, et al. Efficiency of P-glycoprotein-mediated exclusion of rhodamine dyes from multidrug-resistant cells is determined by their passive transmembrane movement rate. Eur J Biochem 1997 248(1) 104—112. 

Although the competition of two substrates for the same P-gp normally results in an inhibitory effect on the P-gp-mediated transport of the substrates, stimulation of P-gp-mediated efflux transport has been reported in some cases. The P-gp-mediated doxombicin efflux out of multidrug-resistant HCT-15 colon cells was significantly increased by some flavonoids (13). Similarly, rhodamine 123 and Hoechst 33342 stimulated the rate of P-gp-mediated transport of each other in P-gp-enriched plasma membrane vesicles isolated from Chinese hamster ovary CHRB30 cells (14). Interestingly, Hoechst 33342 transport was increased by daunorubicin and doxombicin, while rhodamine 123 transport was inhibited by daunombicin and doxombicin (14). These results strongly suggest that molecular mechanisms of P-gp interaction are quite complex and cannot be predicted readily. 

Much less inhibition was found in the MCF7/MDR1 drug-resistant human breast cancer cell line in the presence of same carotenoids as were investigated earlier on the human MDR1 gene-transfected mouse lymphoma cells. As Table 5 shows the, rhodamine accumulation was enhanced only moderately from 1.1 to 2.2 fluorescence activity ratio, which means that the rhodamine uptake was enhanced from 10% to 120% in the human breast cancer cells. On the other hand, some carotenoids such as Zl-neoxanthin, mono-epoxy-a-carotene and 15,15-dehydro-diepoxy-/J-carotene were inactive (Table 5). 

Jaroszewski, J. W., Kaplan, O., and Cohen, J. S. (1990). Action of gossypol and rhodamine 123 on wild type and multidrug-resistant MCF-7 human breast cancer cells 31P nuclear magnetic resonance and toxicity studies. Cancer Res. 50, 6936-6943. 

---