Tissue platinum

Tissue platinum was assayed by atomic absorption spectroscopy to estimate the distribution of infused carboplatin [11, 18]. 

Tissue distribution is similar to that seen with cisplatin with the highest concentrations of platinum in the kidney, liver, skin and tumors [53]. Tissue platinum concentrations were generally 0.5 to 3 fold greater than those observed after cisplatin. However, once platinum is bound to plasma protein its cytotoxicity is substantially reduced [54]. In contrast to the extensively protein binding of cisplatin, carboplatin is only 15 to 25% bound during the initial hours following administration. Renal clearance appears to be the main route... 

The tetroxide has been used to detect fingerprints and to stain fatty tissue for miscroscope slides. The metal is almost entirely used to produce very hard alloys, with other metals of the platinum group, for fountain pen tips, instrument pivots, phonograph needles, and electrical contacts. 

Some elements found in body tissues have no apparent physiological role, but have not been shown to be toxic. Examples are mbidium, strontium, titanium, niobium, germanium, and lanthanum. Other elements are toxic when found in greater than trace amounts, and sometimes in trace amounts. These latter elements include arsenic, mercury, lead, cadmium, silver, zirconium, beryUium, and thallium. Numerous other elements are used in medicine in nonnutrient roles. These include lithium, bismuth, antimony, bromine, platinum, and gold (Eig. 1). The interactions of mineral nutrients with... 

Ruthenium nowadays finds many uses in the electronics industry, particularly for making resistor tracks. It is used as an ingredient in various catalysts and, importantly, in electrode materials, e.g. Ru02-coated titanium elements in the chloralkali industry. Osmium tetroxide is a very useful organic oxidant and, classically, is used as a tissue stain. Both elements are employed in making certain platinum alloys. 

In a typical tumour ECT, a direct current (d.c.) voltage of 8.5 V is applied between two platinum electrodes inserted 3 cm apart in a cancerous tissue (e.g., liver tumour), causing a flow of 30 mA electrolysis current this current is made to flow continuously for... 

Figure 10. Electrode arrangement during the electrochemical treatment (ECT) with low-level direct current one platinum electrode is placed at the center of the tumor, four electrodes with opposite polarity are inserted at the border between the tumor and the surrounding liver tissue. Taken from Turler and coworkers. l...

Several different types of electrodes have been used in this analysis. Conventionally, a platinum (Ft) electrode has been employed in ACh and Ch analysis. Yasumatsu and colleagues (1998) used this method to measure ACh and Ch in tissue extracts and microdialysates, achieving mean concentrations of 0.06 pmol/ 10 pi and 0.64 pmol/10 pi of preoptic or anterior hypothalamus dialysate respectively. Rakovska and colleagues (2003) also analyzed microdialysates with a similar procedure, achieving limits of detection of 500 finol for ACh and 250 finol for Ch. 

The greatest research effort on radiation sensitizers has focused on organic compounds however, platinum complexes conform to the hypotheses for radiation sensitizers since they are electron affinic and react preferentially with the hydrated electron in aqueous solution. Early studies of cisplatin in combination with radiation therapy suggested a synergistic effect in antitumor activity (50,51). Much of the initial data were obtained using cells in tissue culture (52), these data indicated that the potential of cisplatin to inhibit repair of radiation-induced damage to DNA could be an important contributor to the enhanced tumor cell killing seen in vivo by the combination of these two modes of treatment. 

Taylor DM, Tew KD, Jones JD. Effects of cis-dichlorodiammine platinum (II) on DNA synthesis in kidney and other tissues of normal and tumour-bearing rats. EurJ Cancer (Oxford) 1976 12(4) 249-254. 

Reed E, Sauerhoff S, Piorier MC. Quantitation of platinum-DNA binding in human tissues following therapeutic levels of drug exposure—a novel use of graphite furnace spectrometry. Atomic Spectroscopy 1988 9 93-95. 

Another issue with platinum catalysts is that their capacity sometimes fades over time. Several factors are responsible, including a phenomenon similar to the side effects described for medications in chapter 3. Side effects occur when a medication acts on healthy tissue instead of the intended target. With platinum electrodes, the problem is that sometimes unwanted reactions occur at the electrodes. In the oxygen reactions taking place at the cathode, for example, hydroxide (OH) and other molecules sometimes form and bind to the platinum atoms. These molecules cover the platinum atoms and block access to the desired reactant, thereby reducing the catalytic activity. Sometimes the molecules even pull platinum atoms away from the surface, causing serious electrode degradation. 

Dabholkar M, Vionnet J, Bostiek-Bruton F et al. Messenger RNA levels of XPAC and ERCCl in ovarian eaneer tissue eorrelate with response to platinum-based ehemotherapy. J Clin Invest 1994 94 703-708. 

Figure 17-11 Response of an cmperometric glucose electrode with dissolved 02 concentration corresponding to an oxygen pressure of 0.027 bar, which is 20% lower than the typical concentration in subcutaneous tissue. [Data from S.-K. Jung and G. W. Wilson, "Polymeric Mercaptosilane-MocMed Platinum Electrodes lor Elimination of Interfer-ants in Glucose Biosensors," Anal. Chem. 1996,68.591.]...

Several studies on models have been reported, both on the binding of a range of metals to apometallothionein and the design of ligands, particularly with Cys-X-Cys and Cys-X-Y-Cys arrangements as found for metallothionein.1163,1164 All metal derivatives appear to bind in metal-thiolate clusters.1149 Platinum has also been found bound to metallothionein in rat tissues following treatment with cisplatin and the trans isomer.1165... 

Platinum auxiliary electrode Ag/AgCl (3 mol L-1 KC1) reference electrode tissue biosensor as working electrode. 

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