Myocardial tissue preparation for ESR spectroscopy: some methods may cause artifactual generation of signals

It has been suggested that some techniques of tissue preparation for esr spectroscopy may artifactually generate radicals. We have investigated this, together with the possibility that the susceptibility of the tissue to preparation artifacts may be altered by ischaemia and reperfusion. Three different methods of tissue processing have been assessed: (i) freeze-clamping (-196 degrees C), using grooved, aluminium tongs which produce frozen cylinders of tissue (3 mm diameter) which fit directly into esr tubes; (ii) grinding of freeze-clamped tissue with a porcelain pestle and mortar; (iii) lyophilization of ground, freeze-clamped, tissue. Isolated rat hearts (n = 7 or n = 5/group) were subjected to aerobic perfusion (10 min, 37 degrees C), total, global ischaemia (15 min) and reperfusion (30 sec). Hearts were freeze-clamped at the end of each period. Tissue was prepared by each of the three methods and esr spectra recorded at -100 degrees C. In spectra from tissue which had been freeze-clamped only, broad high- and low-spin iron III signals (g = 1.9, g = 2.2-2.9 and g = 4.6) were seen together with a narrow, well-defined signal (g = 2.005), possibly from a semiquinone radical.(ABSTRACT TRUNCATED AT 250 WORDS)