The in Vitro and in Vivo Photoreactivity of Bilirubin: I. Laser-Defined Wavelength Dependence

Abstract

SummaryMonochromatic light was provided by a continuous wave Argon ion laser. We chose to study the in vitro effects of light at 457.9, 465.8, 476.5, 488.0, 501.7, and 514.5 nm as representative of a reasonably evenly spaced samplig across the blue-green spectrum. The in vivo experiments were conducted at 457.9, 476.5, 488.0, and 514.5 nm.In vitro light at 488.0 nm appeared to be more effective than the others studied.After 24 h of irradiance, the in vivo decline in serum bilirubin concentration produced by light at 488.0 nm was one-and-one-half, two, and four times as effective as light at 457.9, 476.5 and 514.5 nm, respectively. By 48 h of exposure, the declines produced by light at 457.9 nm and 488.0 nm are significantly superior to that at 476.5 nm and 514.5 nm, but they do not differ from one another.The photon-induced chemical alteration of bilirubin has been demonstrated by various light sources both in vitro and in vivo. The clinical application of this phenomenon has been widely used as phototherapy in the treatment of neonatal hyperbilirubinemia. Investigations designed to delineate the effective wavelengths have employed broad spectrum light sources and have indicated that irradiance with light of wavelengths of 425-475 nm is maximally effective both in vitro (2,7,8,10, 13,25,31) and in vivo (1,11,17,24,29,33,36). But one study performed in vitro with a relatively narrow spectral source suggested wavelengths at 490 nm might also be efficacious (10). More recently, Lilien et al. (27) have performed experiments that also suggest that wavelengths of light beyond the 425475 nm range are efficacious in vitro.Radiant energies within the 400-500 nm range exhibit potential for inducing damage to tissues. Light from standard fluorescent lamps causes breaks in DNA strands in vitro (3, 35) and increases sister chromatid exchanges and other chromosomal alterations in cultured cells (4,18,21,23,32,35,37). An increased frequency of sister chromatid exchange has been reported in some infants after phototherapy (12). Although we know of no reports regarding any increase in sister chromatid exchange in vivo in response to monochromatic light, the occurrence seems likely; thus, the widespread use of phototherapy has generated concern regarding the potential for long-term mutagenic and carcinogenic effects. Inasmuch as most published data suggest that the offending wavelengths are principally in the ultraviolet range, some recent work has implicated light of wavelengths exceeding 300 nm (9) and, indeed, some alterations appear to occur maximally in response to wavelengths of light between 420-500 nrn (35). Although the magnitude of these latter risks has not been quantitated as they may relate to the clinical setting, it seems desirable to more precisely define the most efficacious wavelengths for the photoalteration of bilirubin that results in its enhanced excretion. This is particularly needed in the design of future phototherapy instruments to be used in the management of neonatal hyperbilirubinemia. Preliminary po...

Quantum Yields for Laser Photocyclization of Bilirubin in the Presence of Human Serum Albumin. Dependence of Quantum Yield on Excitation Wavelength

“…Because of the experimental design, the physiological relevance of that study is questionable: photoisomerization reactions were neglected, photoreactions were allowed to go to high conversion and performed on unstirred solutions in cells of long photochemical pathlength, and samples had higher optical thicknesses at 457.9 and 488.0 nm than at longer wavelengths. The results disagreed with those of several other more detailed studies (Gutcher et al, 1983;Lightner et al, 1980;Raethel, 1975), probably because of a failure to recognize the effects of optical thickness differences. Nevertheless, clinical trials (which did not include a control group of unirradiated infants) have indicated that green lights do have a phototherapeutic effect (Sbrana et al, 1987), though they are not more effective than blue lights (Foschi et al, 1986;Ayyash et al, 1987a, b).…”

“…Our data indicate that blue or blue-green light in the 480-510 nm region is likely to be the best for phototherapy, as suggested by experiments in jaundiced rats (Gutcher et al, 1983) and originally recommended when phototherapy was introduced (Broughton et al, 1965;Cremer et al, 1958). Although lights emitting maximally at the BR absorption maximum (Tan, 1982) are probably not the most effective, there seems to be no compelling scientific reason at present for using narrow-band green lights with peak emission near 525 nm in preference to lights that have better overlap with the long wavelength side of the BR absorption band.…”

Laser Investigation of Bilirubin-Photobilirubin Photoconversion

“…Numerous studies have been done on lysosomal glycosidases but few consistent findings have been reported. Among the most reproducible of the findings on glycosidases is the significant elevation of a-D-glucosidase activity in CF tissues (2)(3)(4)(5)(6)(7). In a previous study we confirmed the fact that neutral a-D-glucosidase activity is significantly elevated in CF sera (2).…”

“…From the clinical point of view the most effective spectral region of BR degradation in the organism is still considered that matching the visible absorption spectrum maximum of BR in vitro (-450 nm). However, recent investigation of BR photodegradation in vitro and in vivo made with monochromatic optical sources (lasers) shows that other spectral regions at longer wavelengths may be more suitable for phototherapy (5,17). The use of lasers for the analysis of the photophysical and photochemical properties of BR and of its photoproducts has been found to be particularly suitable due to their monochromaticity and frequency tunability, which make it possible to show up small differences in the physical and chemical behavior of PBRs.…”

A Prospective Randomized Controlled Study of Phototherapy Using Blue and Blue-Green Light-Emitting Devices, and Conventional Halogen-Quartz Phototherapy

“…15 This cobinding results in a shift in the absorption maximum of bilirubin to longer wavelengths. 17 In addition, it has been noted that the absorption spectrum of bilirubin may be modified when bound to skin constituents 18 and by the filtering action of skin layers. 16 The apparent efficacy of the green fluorescent lamps used in some of these clinical studies can be attributed to the not unimportant contribution of blue light present in these lamps.…”