Activated polymorphonuclear leukocytes increase low-level chemiluminescence of isolated perfused rat lungs.

Low-level chemiluminescence was measured in isolated perfused rat lungs subjected to different types of oxidative stress: perfusion with tert-butyl hydroperoxide (t-BOOH) or stimulation of polymorphonuclear cells (PMN). The time required for t-BOOH-dependent lung chemiluminescence to return to background levels was proportional to the concentration of t-BOOH. From the half times of the decay at different t-BOOH concentrations, we estimated that the lungs metabolize organic peroxides at a rate of 0.045 mM/min. Use of a high dose of t-BOOH (3 mM)or pretreatment of lungs with 1,3-bis(2-chloroethyl)-nitrosourea (100 micrograms/ml) to inhibit glutathione reductase produced chemiluminescence that was much greater and did not decay. Stimulation of 5 x 10(7) PMN with 1 micrograms of phorbol myristate acetate resulted in significant increases in chemiluminescence that occurred in the absence of a significant lung weight gain or measurable lipid peroxidation. Perfusion of isolated lungs with superoxide dismutase (100 U/ml) completely inhibited the chemiluminescence response to PMN activation, whereas treatment with 100 microM U-74389F, a lipid-soluble antioxidant, also significantly decreased PMN-dependent chemiluminescence. Neither catalase (2,000 U/ml) nor 100 microM U-78518F, a water-soluble antioxidant, decreased chemiluminescence after PMN activation. These results indicate that low-level chemiluminescence is a sensitive indicator of oxidative stress in the isolated perfused rat lung and provides a tool for devising and characterizing the effectiveness of antioxidant interventions.

Retinal detachment associated with subthreshold retinopathy of prematurity.

PURPOSE: To report a series of infants who progressed from mild retinopathy of prematurity (ROP) to severe ROP with retinal detachment without demonstrating detectable threshold disease. METHODS: Between January 1993 and August 1998, seven infants at Oregon Health Sciences University, followed in accordance with the Cryotherapy for Retinopathy of Prematurity Study (CRYO-ROP) protocol, progressed to retinal detachment despite documentation that threshold had not been reached. This outlying subset of patients was analyzed and compared to the cohort in the CRYO-ROP study. RESULTS: Six of 7 patients were male, 6 (86%) patients had symmetric disease, and all patients were born outside the study hospital. Mean birth-weight was 877 g and mean gestational age was 26 weeks. Mean postconceptual age at the time of retinal detachment was 41 weeks. Because of bilateral detachment in 3 patients, the total number of study eyes is 10. Failure to achieve threshold resulted from insufficient clock hours or insufficient stage in 2 eyes and lack of plus in 8 eyes. Zone I disease was present in 1 eye. CONCLUSION: Rarely, despite adhering to ROP examination protocol, the retina may detach without demonstrating antecedent threshold disease. Very low birthweight is a factor that may lead to a less predictable course. This study found a lack of plus disease results in failure to reach threshold more often than the occurrence of insufficient clock hours of stage 3 disease. Further study is needed to determine if selected cases of subthreshold ROP may benefit from ablative therapy.

Protein and amino acid oxidation is associated with increased chemiluminescence.

Incubation of 4% bovine serum albumin (BSA) with 1 mM tert-butyl hydroperoxide (t-BOOH) resulted in a peak of chemiluminescence followed by decay to a steady-state level of 18 counts per second above control. When using BSA of differing fatty acid content, the intensity of the initial peak was proportional to fatty acid content, while the steady-state chemiluminescence was independent of lipid content and depended only on BSA concentration. Light emission was inhibited by superoxide dismutase, desferrioxamine, and the antioxidant U-78518F. Oxidation of BSA by neutrophils activated with phorbol myristate acetate also increased chemiluminescence, in a process inhibitable by superoxide dismutase and U-78518F. When adding 1 mM t-BOOH in the presence of 20 microM heme to tryptophan, tyrosine, or to a lesser extent histidine, chemiluminescence correlated with increased oxygen consumption and the appearance of carbonyl derivatives, suggesting that chemiluminescence is a result of the decay to ground level of excited carbonyls. Lysine and glycine, on the other hand, were not oxidized to carbonyls after exposure to t-BOOH and did not emit light or consume significant oxygen during this challenge.