Transcutaneous bilirubinometry: a noninvasive tool for studying newborn jaundiced rats before and after exposure to light

Auditory evoked potentials in a newborn Wistar rat model of hyperbilirubinemia

Introduction

Hyperbilirubinemia is a common health problem in newborns. Its effects can be different according to the level and duration of the hyperbilirubinemia. The toxic effect of bilirubin on the auditory system can be seen as a sensory neural hearing loss or auditory neuropathy spectrum disorder (ANSD).

Objective

The purpose of our study was to determine the effects of toxic bilirubin level on the auditory system by using Auditory Brainstem Response audiometry.

Methods

Rats are used as animal models due to their low cost and easy attainability. Auditory Brainstem Response was used for auditory assessment. In this study, three groups were established: experimental, control and placebo groups.

Results

In the experimental group, which consists of rats with hyperbilirubinemia, sensory neural hearing loss was found bilaterally in 4 rats (66.67%) and unilaterally in 2 rats (16.67%) and auditory neuropathy spectrum disorder was found unilaterally in 1 rat (8.33%). Auditory Brainstem Response thresholds were significantly elevated compared to control and placebo groups (p < 0.05).

Conclusion

Hyperbilirubinemia of newborn rats may result both in sensory neural hearing loss and auditory neuropathy spectrum disorder.

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.