Rhodamine dyes, mitochondrial membrane

Mitochondria are distinct organelles with two membranes. The outer membrane limits the organelle and the inner membrane is thrown into folds or shelves that project inward and are called cristae mitochondriales. The uptake of most mitochondrion-selective dyes is dependent on the mitochondrial membrane potential. Conventional fluorescent stains for mitochondria, such as rhodamine and tetramethylrosamine, are readily sequestered by functioning mitochondria. They are, however, subsequently washed out of the cells once the mitochondrion s membrane potential is lost. This characteristic limits their use in experiments in which cells must be treated with aldehyde-based fixatives or other agents that affect the energetic state of the mitochondria. To overcome this limitation, the research... 

Increase in mitochondrial membrane permeability permeability transition pore opening (PT) decrease in mitochondrial membrane potential (MMP) JC-1 and JC-9 carbocyanine dyes Mito Tracker and MitoFluor dyes TMRME and Rhodamine 123 Flourescent probe, calcein redistribution Radiolabeled deoxyglucose Large changes may not be specifi for apoptosis subtle changes, more characteristic of apoptosis may not be measurable alterations may be reversible... 

The membrane potential of individual cells can be monitored with a fluorescence microscope. For this purpose, however, it is preferable to use a permeable redistribution dye with spectral characteristics that have minimal environmental sensitivity. Thus, the fluorescence intensity will reflect the degree of Nemstian accumulation of dye only and can, therefore, be readily interpreted. The plasma membrane potential can be distinguished from the organelle membrane by simply using the microscope to identify appropriate regions of the cell (44). Rhodamine-123 (Chart III) was introduced as a mitochondrial stain by Chen and co-workers (45-47) it has been used largely in qualitative studies of mitochondrial membrane potential and has been especially effective in flow cytometry applications. 

Our laboratory (44) has synthesized two rhodamine dyes, TMRE (Chart III) and TMRM, that are very similar to rhodamine 123 except the free amino groups are substituted with methyl substituents. This substitution makes the dyes more permeable than rhodamine 123 and also blocks any poorly reversible hydrogen-bonding interactions with anionic sites in the mitochondrial inner membrane and matrix. These qualities combined with... 

Once formed phosphonium salts could have a significant effect on cellular processes, particularly on mitochondrial function. Ph3PMe has been used as a probe to measure membrane potentials, for instance in thyroid cells lymphocytes Escherichia and human granulocytes The lipid-soluble cation distributes itself across the membrane in accordance with the membrane potential Monovalent lipophilic cations which have significant membrane permeability are concentrated in mitochondria. For instance the laser dye Rhodamine 123 has been used as a specific probe for the localisation of mitochondria in living cells It has also been shown to have in vivo antitumour activity ... 

Membrane-permeant fluorescent mitochondrial dyes, such as Rhodamine 123 (Rh 123 Sigma) or 4-Di-2-Asp (Molecular Probes), can be used to aid visualization of nerve terminals in the embryo (Yoshikami and Okun 1984). To label embryos, expose the embryos to the dye (5 pm) for 5 minutes and then remove the excess dye with several washes of saline. View the preparation with an epi-fluorescence attachment and appropriate filters. 

---