Laboratory measurements:
Blood was collected four times in both groups for measurement, using an retrograde cardioplegia cannula -
1. Immediately after entering the cardiopulmonary bypass,
2. 20 min after cross-clampplacement,
3. Immediately before cross-clamp removal, and
4. 20 min after removal of the cross-clamp. Blood samples were stored at -80°C.
Measurement of Serum adenosine deaminase activity: Serum adenosine deaminase activity (ADA) was determined using the spectrophotometric method described byGiuisti, which relies on the indirect calculation of ammonia formation resulting when adenosine deaminase acts in excess of adenosine (5). Results were expressed as units per liter (U/L).
Thiol/disulfide homeostasis tests: Thiol/disulfide homeostasis was measured with the commercially available novel automatic and spectrophotometric technique developed by Erel and Neselioglu (6) (Rel Assay Diagnostics, Turkey).Using this technique, dynamic and reducible disulfide bonds in the samples were reduced to free functional thiol groups by means of sodium borohydride. In order to avoid unused reduced sodium borohydride being reduced to dithionite-2 nitrobenzoic (DTNB), NaBH4 was removed with formaldehyde. Values for native thiol (NT) and total thiol (TT) were calculated following reaction with DTNB. Disulfide (DS) levels were calculated ashalf the difference of the result obtained by subtracting the native thiol value from the total thiol content.
Measurement of paraoxonase activity: The fully automated method developed by Rel Assay Diagnostics (Mega Tıp, Gaziantep, Turkey) was employed to examine serum paraoxonase 1 (PON) activity. This technique involvesparaoxonase activity beingcalculated in medium without NaCl (basal paraoxonase activity) and with NaCl (salt-stimulated paraoxonase activity). Hydrolysis of the paraoxone (diethyl-p-nitrophenylphosphate) is monitored by observing the increase in absorbance at 37-C and 412 nm. The quantity of p-nitrophenolproduced by the hydrolysis is calculated using the molar absorption coefficient 17,000 Mj1cmj1 (at pH 8). Net values with enzymatic activity are obtained by subtracting the basal activity value from the salt-stimulated activity value. The results are expressed as unit per liter, equivalent to the hydrolysis of 1 micromole substrate in one minute and one liter.
Measurement of arylesterase activity: The fully automated method developed by Rel Assay Diagnostics (Mega Tıp, Gaziantep, Turkey) was employed to measure paraoxonasearylesterase form as a result ofrase activity in the serum samples. This technique involves the use of phenyl acetate as a substrate for calculatingarylesterase activity. Phenol and acetic acidphenyl acetate hydrolysis. The phenol that forms thenbinds to 4- aminoantipyrine and potassium ferricyanide, and is measured using the colorimetric method. Arylesterase enzyme activity is calculated from 4000 Mj1cmj1, representing the molar absorption coefficient of the colored complex that forms. The results are expressed as unit per liter, equivalent to the hydrolysis of 1 micromole phenyl acetate in one minute and one liter.
Measurement of xanthineoxidase (XOD): XOD measurement was performed using a microELISA kit and aRel Assay DiagnosticsReader device and washer. This was operated manually, with specimens being automatically washed and read.
Measurement of superoxide dismutase (SOD): SOD was measured automatically on a Selectra (The Netherlands) biochemistry autoanalyzer, using aRel Assay Diagnostics automatic biochemistry kit.
Measurement of Creatine kinase-MB (CK-MB): CK-MB was measured automatically using a Rochechemiluminescence method device and a Rochechemiluminescence kit.
Measurement of Troponın I: Troponin I was measured automatically using a Roche chemiluminescence method device and a Roche chemiluminescence kit.
CPB and cross-clamp times, and lengths of stay in the intensive care unit were recorded. Inotropic support or intra-aortic balloon pump device (for weaning the CPB or in the first 24 hours postoperatively) requirements were also noted.