Fig. 8.

A: superoxide levels in lung tissue in sham-operated control and shunted lambs at 2, 4, and 8 wk of age estimated by electron paramagnetic resonance (EPR) assay using 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine·HCl (CMH), which forms a stable chemical product with superoxide. Superoxide concentrations increased from 2 to 8 wk of age in both sham-operated control and shunted lambs (ANOVA) and were greater in shunted lambs than sham-operated control lambs at each age. B: S-ethylisothiourea hydrobromide (ETU)-mediated inhibition of NOS resulted in almost no change in EPR amplitude of control lambs, whereas shunted lambs showed up to ∼30% reduction in signal, suggesting that uncoupled eNOS contributed to superoxide levels in shunted but not control lambs. n = 5 for each group. Values are means ± SD. *P < 0.05 compared with age-matched sham-operated control; †P < 0.05 compared with previous sham-operated control; §P < 0.05 compared with previous shunt.