Dermal carbon monoxide excretion in neonatal rats during light exposure.

Total body, head, and trunk carbon monoxide (CO) excretion rates were measured separately by gas chromatography in 1- to 7-d-old Wistar rat pups exposed to the dark and to mixed blue (one Special Blue-F20T12/BB) and white (two Cool White-F20T12/CW) fluorescent light or blue light emitting diode (LED) sources. During 48-min cycled exposures to the dark and to either light source, total body CO excretion rapidly increased 1.9- and 1.4-fold, respectively, over dark control levels. When CO excretion rates from the head and trunk were measured separately during exposure to either light source, CO excretion from the head did not change significantly; however, a large mean 4.4-fold increase in CO excretion from the trunk was observed. When light intensity delivered by the blue LED source was varied, we found that trunk CO excretion increased with increasing light intensities. In the presence of riboflavin (10 micromol/kg), total body CO excretion increased 2.8- and 2.1-fold during exposure to the mixed fluorescent light and blue LED sources, respectively. We conclude that light-induced elevations in total body CO excretion may be caused by transdermally excreted CO, which is most likely produced through endogenous photosensitizer-mediated photooxidation of dermal biomolecules.