Intracellular electrochemistry

Early studies by Meulemans et al. used differential pulse voltammetry (see Chapter 11) to measure the concentration of electroactive drugs in the cytoplasm of cholinergic neurons of Aplysia californica and to determine rates of cellular uptake and clearance (108). Another report by Meulemans et al. described a needle tipped glass insulated platinum electrode for detection of intracellular serotonin in metacerebral neurons from Aplysia (109). Again differential pulse voltammetry was used to measure intracellular concentration of serotonin after cell stimulation, after injection of serotonin into the cell, and after extracellular treatment with tryptophan, a serotonin precursor. Serotonin concentration in resting untreated cells was determined to be 0.94 0.61 mM. Chen et al. have also used platinum electrodes with multiple pulse voltammetry to measure dopamine levels in the giant dopamine neuron of Planorbis comeus (110). 

Effects of drug treatment on cytosolic levels of catecholamines and total oxidizable species were also investigated. Reserpine, an inhibitor of the vesicular monoamine transporter (this transporter loads vesicles with catecholamines), had no effect on the amount 

Storage. Intracellular patch amperometry may prove valuable in elucidating the coupling of the neurotransmitter synthesis, storage, and release processes. 

Dahlstrom, J. Haggendal, T. HokfelL Acta Physiol. Scand. 67, 289 (1966). 

G Alvarez de Toledo, R. Femandez-Chacon, J. M. Fernandez, Nature 363, 554 (1993). 

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All biological life (disregarding viruses that only show some properties of life) is composed of cells or collections of cells. At the most basic functional level, a cell consists of a collection of internal structures that are immersed in intracellular fluid and separated from the outside by a cell membrane, which is also called plasma membrane or plasmalemma. There are other membranes of great importance in biology, e.g., those surrounding the nucleus of an eukaryote cell, but this entry is focused on the electrochemistry of the... 

In the amperometric mode all easily oxidized molecules (including catechols) are detected whereas in the voltammetric mode catecholamines can be preferentially measured. Because membrane capacitance is recorded simultaneously, it is possible to determine if exocytosis is taking place and how it affects cytosohc catecholamine concentration in real time. Figure 17.1.16 shows representative voltammetric data for intracellular patch electrochemistry. 

Figure 17.1.15 Schematic diagram of the intracellular patch electrochemistry setup. Amp 1, Amp 2, Amplifiers GND, electric ground CFE, carbon fiber electrode PP, patch pipette. Reproduced with...

Cohen A, Martin M, Schwartz E (1984) Depletion of excessive liver iron stores with desferrioxamine. Br J Haematol 58 369-373 Conrad ME (1993) Excess iron and catastrophic illness. Am J Hematol 43 234-236 Conrad ME, Umbreit JN (1993) Iron absorption - the mucin-mobilferrin-integrin pathway. A competitive pathway for metal absorption. Am J Hematol 42 67-73 Conrad ME, Umbreit JN, Peterson RDA, Moore EG, Harper KP (1993) Function of integrin in duodenal mucosal uptake of iron. Blood 81 517-521 Cooper SR, McArdle JV, Raymond KN (1978) Siderophore electrochemistry relation to intracellular iron release mechanism. Proc Natl Acad Sci USA 75 3551-3554... 

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