Superoxide dismutase (SOD) and catalase (CAT), enzymes that degrade superoxide anion and hydrogen peroxide, respectively, reduce size of infarction in anesthetized, open-chest dogs subjected to coronary occlusion followed by reperfusion. To evaluate potential protective effects of these enzymes in conscious animals, three groups of dogs were instrumented at sterile surgery with a hydraulic occluder on the left circumflex (LCX) coronary artery, sonomicrometers to measure regional wall thickness, and catheters to monitor arterial and left ventricular pressures. Ten to 14 days after surgery, the animals were sedated with morphine sulfate (0.5 mg/kg). The LCX artery was occluded for 3 hr by inflation of the hydraulic cuff. Infusions of SOD (n = 7), CAT (n = 6), or saline (control group, n = 7) were begun 15 min before reperfusion and lasted for 45 min of reperfusion. The doses of SOD and CAT were 5 mg/kg, dissolved in 60 ml of saline, and infused at a rate of 1 ml/min. Myocardial blood flow was measured with tracer-labeled microspheres (15 gm diameter) before occlusion, after 5 to 10 min of occlusion, after 150 min of occlusion, and 5 to 10 min after reperfusion. Size of infarction was measured 24 hr later by dual-perfusion staining with Evans blue and triphenyl tetrazolium. Size of infarction (expressed as a percentage of area at risk) did not differ significantly among the three groups: control, 32 + 17% (mean ± SD); SOD, 38 + 17%; CAT, 27+ 17%. Hemodynamic parameters and myocardial blood flows (measured before infusion of any agents) were not significantly different among the three groups. Serum SOD levels in SOD-treated dogs were 19 ± 2 gg/ml at the onset of reperfusion and 29 ± 3 gg/ml at the end of the infusion. Blood assays collected after infusion showed a monoexponential decay of SOD levels with a half-life of 22 ± 6 min. We conclude that myocardial protection by SOD or CAT is model dependent. In conscious dogs subjected to 3 hr of coronary occlusion followed by reperfusion, SOD and CAT failed to alter size of infarction.

To evaluate the degree and lateral extent of dysfunction in nonischemic myocardium adjacent to ischemic muscle, we measured systolic wall thickening with sonomicrometers during circumflex coronary occlusion in 12 anesthetized, open-chest dogs. The locations of the wall thickness measurements relative to the perfusion boundary were determined with myocardial blood flow (microspheres) maps constructed from multiple, small tissue samples. Five minutes after circumflex occlusion, systolic wall thickening in the central ischemic zone decreased from 3.00 +/- 0.61 (mean +/- SD) mm to -0.61 +/- 0.36 mm (P less than 0.01). In nonischemic myocardium greater than 10 mm from the perfusion boundary, systolic wall thickening increased from 2.56 +/- 0.57 to 3.24 +/- 0.72 mm (P less than 0.01). In nonischemic myocardium within 10 mm of the perfusion boundary, systolic wall thickening was slightly but significantly reduced compared with control (2.72 +/- 0.80 to 2.44 +/- 0.79 mm, P less than 0.05), supporting the concept of regional dysfunction in nonischemic myocardium at the lateral borders of an ischemic area. Sigmoid curves were fitted to the data to model changes in wall thickening as a continuous function of distance from the perfusion boundary. This allowed estimation of the extent of dysfunction into nonischemic myocardium which averaged less than 8 mm (approximately 30 degrees of endocardial circumference) at one border. The level of functional impairment in this zone was relatively modest, and systolic wall thickening in the immediate border area was reduced more than 50% from control only in tissue characterized by a blood supply of mixed ischemic and nonischemic origin. We conclude that a functional border zone exists lateral to an acutely ischemic area, but measurement of regional function produces relatively small exaggeration of the size of the acutely ischemic zone if severe reduction in mechanical performance is used to define the extent of the ischemic area.

The use of quantitative gene expression analysis for the diagnosis, prognosis, and monitoring of disease requires the ability to distinguish pathophysiological changes from natural variations. To characterize these variations in apparently healthy subjects, quantitative real-time PCR was used to measure various immune response genes in whole blood collected from blood bank donors. In a single-time-point study of 131 donors, of 48 target genes, 43 were consistently expressed and 34 followed approximately log-normal distribution. Most transcripts showed a limited dynamic range of expression across subjects. Specifically, 36 genes had standard deviations (SDs) of 0.44 to 0.79 cycle threshold (C(T)) units, corresponding to less than a 3-fold variation in expression. Separately, a longitudinal study of 8 healthy individuals demonstrated a total dynamic range (> 2 standard error units) of 2- to 4-fold in most genes. In contrast, a study of whole blood gene expression in 6 volunteers injected with LPS showed 15 genes changing in expression 10- to 90-fold within 2 to 5 h and returning to within normal range within 21 hours. This work demonstrates that (1) the dynamic range of expression of many immune response genes is limited among healthy subjects; (2) expression levels for most genes analyzed are approximately log-normally distributed; and (3) individuals exposed to an infusion of bacterial endotoxin (lipopolysaccharide), show gene expression profiles that can be readily distinguished from those of a healthy population. These results suggest that normal reference ranges can be established for gene expression assays, providing critical standards for the diagnosis and management of disease.

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