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In this paper instrumental methods of carbon dioxide (CO₂) detection in biological material were compared. Using cis-[Cr(C₂O₄)(pm)(OH₂)₂]⁺ cation as a specific molecular biosensor and the stopped-flow technique the concentrations of CO₂ released from the cell culture medium as one of final products of pyruvate decomposition caused by hydrogen peroxide were determined. To prove the usefulness of our method of CO₂ assessment in the case of biological samples we investigated protective properties of exogenous pyruvate in cultured osteosarcoma 143B cells exposed to 1 mM hydrogen peroxide (H₂O₂) added directly to culture medium. Pyruvic acid is well known scavenger of H₂O₂ and, moreover, a molecule which is recognized as one of the major mediator of oxidative stress detected in many diseases and pathological situations like ischemiareperfusion states. The pyruvate's antioxidant activity is described as its rapid reaction with H₂O 2, which causes nonenzymatic decarboxylation of pyruvate and releases of CO₂, water and acetate as final products. In this work for the first time we have correlated the concentration of CO₂ dissolved in culture medium with pyruvate's oxidant-scavenging abilities. Moreover, the kinetics of the reaction between aqueous solution of CO₂ and coordinate ion, cis-[Cr(C₂O₄)(pm)(OH₂)₂]⁺ was analysed. The results obtained enabled determination of the number of steps of the reaction studied. Based on the kinetic equations, rate constants were determined for each step.

A short chain synthetic analogue of lipid hydroperoxides was used to overload glutathione peroxidase (GPx) in human choriocarcinoma cell line JAR cells. Cells exposed to 100 microM tBuOOH displayed a 40% reduction in ATP level and significantly increased in membrane permeability, visualised by the lactate dehydrogenase (LDH) release into the extracellular medium. The intracellular level of oxygen free radicals measured as an oxidation of the dichlorodihydro-fluorescein diacetate (H2DCF-DA) significantly increased after 2 hours of cell exposition to 100 microM tBuOOH. Concomitantly MDA, 4-HNE level increased to 2 nmol/mg of cell protein after 2 hours. Mitochondria stained with MitoTracker Red CMXRos displayed a filamentous appearance in control cells but changed into granular less energised organelles after exposition to tBuOOH. Collectively, the above results indicate the importance of the contribution of oxidative stress in the development of pre-eclampsia.

For the first time, a direct sensitive method of *NO(2) detection and measurement in biological material has been established. It is based on the interaction of this radical with the coordination compound of Cr(III) with aminodeoxysugar as biosensor. Our new method makes it possible to precisely assess *NO(2) level in experimental acute necrotizing pancreatitis induced by L-arginine, where oxidative and nitrosative stresses are supposed to play a key role in the pathomechanism of the disease. As much as 20 nmol of *NO(2)/mg protein was detected which correlated with severe deterioration of pancreatic acinar cell ultrastructure. Protective effect of superoxide radical scavenger 4-OH-TEMPO expressed as *NO(2) level decrease confirmed by preserved acinar cell ultrastructure and decreased pancreatic amylase release to blood serum is demonstrated. This study reveals a possible pathomechanism of L-arginine induced acute pancreatitis.