Non-exposed Lens Research Articles

Expression of active caspase 3 in the rat lens after in vivo exposure to subthreshold dose of UVR-B

PurposesThe aim of this study is to investigate the time evolution of active caspase 3 within first 120 h in the rat lens after in vivo exposure to subthreshold dose of UVR-B.MethodsTwenty three six-week-old female albino Sprague-Dawley rats were exposed to subthreshold dose (1 kJ/m2) of UVR-B unilaterally and sacrificed at 24, 41, 70 and 120 h after exposure. Lenses were enucleated and active caspase 3 was detected by Western Blot. The time evolution of active caspase 3 was then plotted as a function of relative mean difference in active caspase 3 between exposed and nonexposed lenses.ResultsThere is expression of active caspase 3 in both exposed and nonexposed lenses but there is no difference in relative mean difference in active caspase 3 between exposed and nonexposed lenses in all four postexposure groups.ConclusionsExposure to subthreshold dose of UVR-B does not induce apoptosis in the rat lens in vivo within first 120 h though there is a non-significant increase of active caspase 3 at 120 h. Increase in sample size might reduce the variation level in expression of active caspase 3 in the rat lenses.

Exposure to subthreshold dose of UVR‐B does not induce increase in caspase 3 mRNA expression in the rat lens in vivo within first 24 hours

Aims/Purpose: The aim of this study is to investigate the time evolution of caspase 3 mRNA expression within first 24 h in the rat lens after in vivo exposure to subthreshold dose of UVR‐B.Methods: Twelve six‐week‐old female albino Sprague–Dawley rats were exposed to subthreshold dose (1 kJ/m2) of UVR‐B unilaterally and sacrificed at 1, 8, 16 and 24 h after exposure. Lenses were enucleated and caspase 3 mRNA expression was detected by qRT‐PCR. The time evolution of caspase 3 mRNA expression was then plotted as a function of mean ratios in caspase 3 mRNA expression between exposed and contralateral nonexposed lenses.Results: There is no difference in mean ratios in caspase 3 mRNA expression between exposed and nonexposed lenses in all four postexposure groups.Conclusions: Exposure to subthreshold dose of UVR‐B does not induce increase in caspase 3 mRNA expression in the rat lens in vivo within first 24 h.

Exposure to subthreshold dose of UVR‐B does not induce apoptosis in the rat lens in vivo during the first 24 hours

AbstractPurpose: The aim of this study is to investigate the time evolution of active caspase 3 in the rat lens after in vivo exposure to subthreshold dose of UVR‐B.Methods: Twenty six‐week‐old female albino Sprague–Dawley rats were exposed to subthreshold dose (1 kJ/m2) of UVR‐B unilaterally and sacrificed at 1, 8, 16 and 24 h after exposure. Lenses were enucleated and active caspase 3 protein was detected by Western Blot. The time evolution was then plotted as a function of relative mean difference in active caspase 3 between exposed and nonexposed lenses.Results: There is expression of active caspase 3 in both exposed and nonexposed lenses but there is no difference in relative mean difference in active caspase 3 between exposed and nonexposed lenses in all four postexposure groups.Conclusions: Exposure to subthreshold dose of UVR‐B does not induce apoptosis in the rat lens in vivo within first 24 hours. Apoptosis occurs in the rat lens independently from the exposure to subthreshold dose of UVR‐B.

Exposure to subthreshold dose of UVR-B induces apoptosis in the lens epithelial cells and does not in the lens cortical fibre cells.

The aim of this study was to investigate in which part of the lens invivo exposure to subthreshold dose of UVR-B radiation induces apoptosis. Twenty 6-week-old female albino Sprague-Dawley rats were exposed to subthreshold dose (1kJ/m2 ) of UVR-B unilaterally and killed at 120hr after exposure. Lenses were enucleated and dissected on three regions: the lens epithelium, the cortex and the nucleus. The lens nucleus then was removed. Apoptosis markers p53 and caspase 3 were used to study apoptosis in the lens regions. qRT-PCR and Western blot were utilized to analyse the lenses. TP53 and CASP3 mRNA expressions are increased in exposed lenses, both in the lens epithelium and in the cortex regions, in relation to non-exposed lenses. Expression of p53 protein is increased in exposed lens epithelium in relation to non-exposed lens epithelium. Caspase 3 protein is expressed in exposed lens epithelial cells, while it is not expressed in non-exposed lens epithelial cells. p53 and caspase 3 proteins are not expressed in either exposed nor non-exposed lens fibre cells. Exposure to UVR-B increases mRNA transcription of apoptosis marker p53 invivo in both regions of the lens and of apoptosis marker caspase 3 in the lens cortex. Exposure to UVR-B increases p53 and caspase 3 proteins expression just in the lens epithelium. In vivo exposure to subthreshold dose of UVR-B induces apoptosis in the lens epithelial cells and does not in the lens fibre cells.

Time evolution of active caspase‐3 labelling after in vivo exposure to UVR‐300 nm

To determine the time evolution of active caspase-3 protein expression in albino rat lens after in vivo exposure to low-dose UVR-300 nm, as detected by immunofluorescence. Forty Sprague-Dawley rats were unilaterally exposed in vivo to 1 kJ/m(2) UVR-300 nm for 15 min. At 0.5, 8, 16 and 24 hr after the UVR exposure, the exposed and contralateral nonexposed lenses were removed and processed for immunohistochemistry. Three mid-sagittal sections from each lens were stained. The cells labelled for active caspase-3 in each section of both the exposed and nonexposed lenses were counted and recorded three times. The difference of the proportion of labelling between the exposed and contralateral nonexposed lenses within each animal was calculated. The differences of active caspase-3 labelling at four different time-points after exposure were used to determine the time evolution of active caspase-3 expression. Caspase-3 expression was higher in the exposed than in contralateral nonexposed lenses. The mean difference between the exposed and contralateral nonexposed lenses, including all lenses from all time intervals, was 0.12 ± 0.01 (= CI 95%). The mean differences between the exposed and contralateral nonexposed lenses were 0.11 ± 0.02, 0.13 ± 0.02, 0.14 ± 0.01 and 0.09 ± 0.03 (= CI 95%) for the 0.5-, 8-, 16- and 24-hr time groups, respectively. The orthogonal comparison showed no difference in the expression of active caspase-3 between the 0.5- and the 24-hr groups (Test statistic 1.50, F1,36 = 4.11, p < 0.05) or between the 8- and the 16-hr groups (test statistic 0.05, F1,36 = 4.11, p < 0.05). There was a difference when comparing the 0.5- and 24-hr groups to the 8- and 16-hr groups (test statistic 7.01, F1,36 = 4.11, p < 0.05). The expression of active caspase-3 in the lens epithelium increases after UVR exposure. There is a peak of expression approximately 16 hr after the exposure.

Regulation of Eaf2 in mouse lens cells apoptosis induced by ultraviolet radiation.

To investigate the regulation of Eaf2 protein in mouse lens cells apoptosis induced by ultraviolet (UV) radiation. An eye of Eaf2 gene knockout mice or normal control mice was exposed to UV radiation, and the other one was non-exposed. All of lenses were analyzed by TUNEL and caspase 3 activity assays to determine the difference of the apoptosis induced by UV radiation. In addition, exposed and non-exposed lenses were analyzed by quantified p53 expression and real-time reverse transcription-polymerase chain reaction (RT-PCR) of Bax, Bid, Apaf-1, Puma and Noxa, to compare Eaf2 gene knockout mice and normal control mice. UV radiation caused apoptosis of lens cells in normal control mice and Eaf2 knockout mice. Activity of caspase 3 was significantly higher in normal control mice than Eaf2 knockout mice. Expression of p53 protein was significantly higher in lenses exposed to UV radiation than nonexposed lenses, but was similar between Eaf2 gene knockout mice and normal control mice in the same UV condition. After exposing to UV radiation, the analysis of real-time RT-PCR demonstrated that mRNA levels of Puma and Noxa were significantly higher in lenses of normal control mice than Eaf2 gene knockout mice, and that mRNA levels of Bax, Bid and Apaf-1 were not significantly different between gene knockout mice and normal control mice. Eaf2 increases lens cells apoptosis induced by ultraviolet radiation. And Eaf2 up-regulates expression of the Puma and the Noxa to act on lens cells apoptosis after UV radiation.

Dose-response relationship for α-tocopherol prevention of ultraviolet radiation induced cataract in rat

The purpose of this study is to establish the dose response relationship for α-tocopherol protection of ultraviolet radiation (UVR) induced cataract in the rat. Four groups of 20 six-week-old albino Sprague Dawley rats received 5, 25, 50, and 100 IU/day α-tocopherol, whilst another group of 20 rats without any α-tocopherol feeding was the control group. After 4 weeks of feeding, each rat was unilaterally exposed to 8 kJ/m 2 UVR-300 nm for 15 min. At 1 week after exposure, the rats were sacrificed and lens light scattering was measured quantitatively. Lens total reduced (GSH) and oxidized (GSSG) glutathione; glutathione reductase (GR) and peroxidase (GPx) were determined spectrophotometrically. The UVR-exposed lenses in the α-tocopherol fed groups developed superficial cataract, whereas lenses in the control group developed cortical and equatorial opacities. Light scattering in lenses from the α-tocopherol-supplemented rats was lower than in lenses from the control group. The difference of light scattering between the exposed and contralateral non-exposed lens decreased with increasing doses of α-tocopherol to an asymptote level. UVR-exposure caused a significant depletion of lens GSH in rats without or at low α-tocopherol supplementation. The depletion of GSH became less with higher α-tocopherol supplementation. There was no detectable difference in lens GSSG, GR or GPx at any level of α-tocopherol supplementation. Orally administered α-tocopherol dose dependently protects against UVR-induced cataract. The protection is associated with an α-tocopherol dose-dependent GSH depletion secondary to UVR exposure. UVR-induced light scattering only occurs if the GSH depletion exceeds a threshold.

Response of p53, capsase 3 and gadd45 genes in the rat lens to in vivo exposure to UV‐B radiation

Abstract Purpose To study the transcriptional induction of p53, caspase 3 and gadd45 genes in the rat lens by in vivo exposure to double threshold UVR‐B around 300 nm. Methods Forty 6‐week‐old female albino Sprague‐Dawley rats were exposed to double threshold dose (8 kJ/m2) UVR (λmax = 300 nm) unilaterally for 15 minutes. The animals were sacrificed at 1, 5, 24 and 120 h following the exposure to UVR‐B. p53, caspase 3 and gadd45 mRNA expression of the lenses was analysed by quantitative RT‐PCR. Data were analysed using one‐way ANOVA. Results p53 is downregulated in exposed lenses in 1 h and 5 h groups and upregulated in 24 h and 120 h groups. Caspase 3 is downregulated in exposed lenses in 1, 5 and 24 h groups and upregulated in 120 h group. No difference in gadd45 mRNA expression between exposed and nonexposed lenses was found in all time intervals. Conclusion p53 mRNA increased expression precedes caspase 3 mRNA increased expression in the rat lens after in vivo UVR‐B exposure. UVR‐B exposure did not induce transcription of DNA damage repair gene gadd45 in the lens up to 120 h.

Evolution of damage in the lens after in vivo close to threshold exposure to UV-B radiation: Cytomorphological study of apoptosis

The purpose of the present study was to investigate cataractogenesis and recovery of lens damage after in vivo close to threshold ultraviolet (UV)-B radiation around 300 nm. Eighty six-week-old albino Sprague–Dawley rats were familiarized to a rat restrainer five days prior to exposure. Groups of non-anesthetized rats were exposed unilaterally to 8 kJ/m 2 UVR-300 nm. The animals were sacrificed at 1, 7, 48 and 336 h following exposure. The lenses were extracted for imaging of dark-field lens macro anatomy and measurement of intensity of forward lens light scattering to quantify lens opacities. Three exposed lenses and one non-exposed lens from each time interval were examined with light and transmission electron microscopy (TEM). Macro anatomy and lens light scattering revealed that all contralateral non-exposed lenses were clear. The degree of lens opacity (difference in lens light scattering between exposed and non-exposed lenses) increased during the 336 h, reaching a plateau towards the end of the observation period. Light microscopy and TEM demonstrated that apoptotic features appeared in the epithelium already 1 h after UVR exposure, and small vacuoles were seen in the outer cortex. Epithelial damage occurs during the first 48 h after exposure and is followed by regenerative repair at 336 h post-exposure. Apoptotic epithelial cells were phagocytized by adjacent epithelial cells. Cortical fiber cells exhibited increasing damage throughout the observation period without any clear repair after 336 h. In conclusion, acute UVR-induced cataract is partly a reversible. Lens epithelium is a primary target for UVR exposure. Damage to cortical fiber cells remained irreversible.

Impact of iris pigment and pupil size in ultraviolet radiation cataract in rat

To investigate the effect of iris pigment and pupil size in ultraviolet radiation (UVR)-induced cataract. Brown-Norway rats (pigmented) and Fischer-344 rats (non-pigmented) were unilaterally exposed in vivo to 5 kJ/m(2) UVR. Each strain was split into two groups, each receiving either mydriatic (tropicamide) or miotic (pilocarpine) eye-drops. One week after exposure, the degree of ocular inflammation and damage in the anterior segment was determined. The lenses were extracted, photographed and the degree of forward light scattering (cataract) was quantified. The cataract types differed between the two strains. All Fischer rats developed macroscopically identifiable UVR cataract while only 41% of Brown-Norway rats did so. All groups except the miotic Brown-Norway developed significant light scattering. The Fischer rats developed 3-4-fold more lens light scattering than the Brown-Norway rats. The miotic Fischer group exhibited significantly more light scattering than the mydriatic Fischer group. There was no significant difference in light scattering between the two Brown-Norway groups. There was a correlation between ocular inflammation and degree of light scattering, with Brown-Norway rats exhibiting less inflammation and lens light scattering. Pigmented rats develop less UVR cataract and less ocular inflammation than non-pigmented rats. Pupil size plays a smaller role in UVR cataract development in pigmented rats than in non-pigmented. The role of UVR-induced ocular inflammation in cataract development is still ambiguous.

Evolution of light scattering and redox balance in the rat lens after in vivo exposure to close-to-threshold dose ultraviolet radiation

To investigate the evolution of cataract development and glutathione redox balance in the rat lens after in vivo close-to-threshold dose exposure to ultraviolet radiation (UVR) around 300 nm. Three groups of 10 Sprague-Dawley rats were unilaterally exposed to 8 kJ/m² UVR-300 nm for 15 min, and a fourth group of 10 rats was kept without UVR exposure as nonexposed control animals. The exposed animals were killed at 1, 3 and 7 days after exposure. Both lenses from all animals were extracted and photographed and the intensity of forward light scattering was measured quantitatively. Thereafter, the lenses were homogenized. The concentration of reduced glutathione (GSH) and oxidized glutathione (GSSG), and the activity of glutathione reductase (GR) and glutathione peroxidase (GPx), respectively, were determined spectrophotometrically. The mean paired differences between exposed and nonexposed lenses were used as primary data in the statistical analyses. All exposed lenses developed cataract. Lens light scattering increased throughout the 7 days after UVR exposure. GSH concentration and GPx rate transiently increased at 1 day after exposure and then decreased throughout follow-up, with GSH concentration having a negative balance at the end. GSSG concentration and GR activity did not change after UVR exposure. In vivo close-to-threshold UVR exposure induces a gradual increase in rat lens opacification/cataract development and time dependently alters the redox balance in the lens.

Drinking water supplementation with ascorbate is not protective against UVR‐B‐induced cataract in the guinea pig

To study if ascorbate supplementation decreases ultraviolet radiation (UVR)-induced cataract development in the guinea pig. Sixty 6-9-week-old pigmented guinea pigs received drinking water supplemented with or without 5.5 mm l-ascorbate for 4 weeks. After supplementation, 40 animals were exposed unilaterally in vivo under anaesthesia to 80 kJ/m(2) UVR-B. One day later, the animals were killed and lenses were extracted. Degree of cataract was quantified by measurement of intensity of forward lens light scattering. Lens ascorbate concentration was determined with high-performance liquid chromatography (HPLC) with UVR detection at 254 nm. Twenty animals were used as non-exposed control. Supplementation increased lens ascorbate concentration significantly. In UVR-exposed animals, mean 95% confidence intervals (CIs) for animal-averaged lens ascorbate concentration (micromol/g wet weight lens) were 0.54 +/- 0.07 (no ascorbate) and 0.83 +/- 0.05 (5.5 mm ascorbate). In non-exposed control animals, mean 95% CIs for animal-averaged lens ascorbate concentration (micromol/g wet weight lens) were 0.72 +/- 0.12 (0 mm ascorbate) and 0.90 +/- 0.15 (5.5 mm ascorbate). All non-exposed lenses were devoid of cataract. Superficial anterior cataract developed in all UVR-exposed lenses. The lens light scattering was 39.2 +/- 14.1 milli transformed equivalent diazepam concentration (m(tEDC)) without and 35.9 +/- 14.0 m(tEDC) with ascorbate supplementation. Superficial anterior cataract develops in lenses exposed to UVR-B. Ascorbate supplementation is non-toxic to both UVR-B-exposed lenses and non-exposed control lenses. Ascorbate supplementation does not reduce in vivo lens forward light scattering secondary to UVR-B exposure in the guinea pig.

Dose dependent cataractogenesis and Maximum Tolerable Dose (MTD2.3:16) for UVR 300 nm-induced cataract in C57BL/6J mice

The purpose of the present study was to investigate the in vivo dose response function for UVR 300nm-induced cataract in the C57BL/6J mouse lens and to establish a cataract threshold estimate expressed as Maximum Tolerable Dose (MTD2.3:16) for UVR 300 nm-induced cataract in the C57BL/6J mouse lens. Knowledge of the MTD2.3:16 in the C57BL/6J mouse will permit quantitative in vivo comparison of UVR-B threshold sensitivity of knockout mice, e.g. animals deficient in key antioxidative enzymes or mice suffering from genetically predetermined eye disease, to wild type animals. Eighty C57BL/6J mice were divided into four dose groups. The animals were exposed unilaterally to 0, 2, 4, or 8kJ/m2 UVR 300nm for 15min (n=20). The radiation output of the UVR-source had λmax at 302.6nm with 5nm full width at half maximum. Two days after exposure cataract was quantified as forward lens light scattering intensity in the exposed and the contralateral non-exposed lens. Morphological lens changes were documented using grid and dark field illumination photography. MTD2.3:16 was estimated from the forward light scattering measurements. Two days after exposure mainly anterior subcapsular but also cortical and nuclear cataract developed in lenses that had received 2, 4, and 8kJ/m2 UVR 300nm. Forward light scattering intensity increased with increasing UVR 300nm dose. MTD2.3:16 for the mouse lens was estimated to 2.9kJ/m2 UVR 300nm. Lens light scattering intensity in the C57BL/6J mouse lens increases with UVR 300nm in vivo dose in the range 0–8kJ/m2. The MTD2.3:16 of 2.9kJ/m2 in the C57BL/6J mouse lens determined here, is essential to quantify and compare in vivo the impact of genetic modulation on lens susceptibility to oxidative stress and plan dose-ranges in future investigations of UVR 300nm-induced cataract pathogenesis.

Biological Response in Various Compartments of the Rat Lens after In Vivo Exposure to UVR-B Analyzed by HR-MAS1H NMR Spectroscopy

The purpose of the present study was to investigate metabolic changes in different compartments of the rat lens (anterior, nuclear, posterior, and equatorial) after exposure to an acute double threshold dose of ultraviolet-B radiation (UVR-B) by using high-resolution magic angle spinning (HR-MAS) (1)H nuclear magnetic resonance (NMR) spectroscopy and pattern recognition (PR) METHODS: methods. One eye in each of 28 6-week-old female albino Sprague-Dawley rats was exposed to in vivo 7.5 kJ/m2 UVR-B for 15 minutes. The contralateral eye was left unexposed. One week after irradiation, all rats were killed, and both lenses were isolated. Each lens was cored by a trephine, and the cylinder was sliced into three portions (anterior, nuclear, and posterior). The lens material that remained after the coring process was analyzed as the equatorial region. Analysis of lens metabolism was performed by HR-MAS 1H NMR spectroscopy (14.1 T; Avance DRX600; Bruker BioSpin GmbH, Rheinstetten, Germany), and the metabolic profiles were statistically analyzed by the PR method of principal component analysis (PCA). Metabolic differences were detected among the compartments in the lens, both in samples from the contralateral nonexposed lenses and in samples from lenses exposed to in vivo UVR-B. In the rat lens, exposure to UVR-B caused changes in GSH, phosphocholine, myo-inositol, succinate, formate, and adenosine triphosphate (ATP)/adenosine diphosphate (ADP) and in levels of the amino acids phenylalanine, taurine, hypo-taurine, tyrosine, alanine, valine, isoleucine, and glutamate, that varied among lens compartments. HR-MAS 1H NMR spectroscopy, combined with PR methods (PCA), is effective for analysis of separate parts of the intact rat lens. To understand the biochemistry of the lens, it is important to divide the lens into sections, representing functionally and anatomically distinct compartments.

Maximum tolerable dose for avoidance of cataract after repeated exposure to ultraviolet radiation in rats

The purpose of the present study was to determine the impact of inter-exposure interval between repeated equivalent exposures of ultraviolet radiation (UVR) on threshold accumulated dose for cataract development. Female Sprague–Dawley rats were randomly divided into 5 inter-exposure interval groups with 20 rats in each group. The inter-exposure intervals were 6 h, 1, 3, 9 and 30 days respectively. Each inter-exposure interval group was divided into 5 dose-subgroups. Only one eye of each rat was exposed to ultraviolet radiation (λ max = 300 nm). The total dose incident on the cornea, in each subgroup varied between 0 ∼ 10 kJ/m 2. One week after the second exposure, the rats were sacrificed and both lenses were extracted. The intensity of forward light scattering was measured and macroscopic morphology was documented. Maximum tolerable dose (MTD) for each inter-exposure interval was estimated based on the experimentally determined dose-response function. The difference of intensity of light scattering between exposed and contralateral non-exposed lens decreased as a function of inter-exposure interval between the two equivalent exposures. The accumulated MTD 2.3:16 was 5.3, 5.1, 5.4, 5.8, and 6.0 kJ/m 2 UVR-B for the 6 h, 1, 3, 9 and 30 day inter-exposure interval between the two exposures, respectively. The shorter the inter-exposure interval between two subsequent exposures, the more damage. The time constant for repair of lens damage after in vivo exposure to close to threshold dose was estimated to be eight days and the fraction of repairable damage to be 20%. The accumulated threshold dose for damage after two repeated equivalent exposures to UVR-B increases as a function of inter-exposure interval up to at least 30 days inter-exposure interval.

Ultraviolet radiation‐B‐induced cataract in albino rats: maximum tolerable dose and ascorbate consumption

To investigate the maximum tolerable dose (MTD) for cataract induced by ultraviolet radiation-B (UVB) in 7-week-old albino rats and to study the effect of UVB eye exposure on lens ascorbate content. Fifty 7-week-old albino Sprague Dawley rats were unilaterally exposed in vivo to 300-nm UVB under anaesthesia, receiving 0, 0.25, 3.5, 4.3 and 4.9 kJ/m(2). The MTD was estimated based on lens forward light scattering measurements. Lens ascorbate content was determined in the processed lens using high performance liquid chromatography with UVR detection. Animals exposed to UVB doses >or=3.5 kJ/m(2) developed cortical cataracts. The MTD for avoidance of UVB-induced cataract was estimated to 3.01 kJ/m(2). UVB exposure decreased lens ascorbate concentration in the exposed lens in line with UVB dose, H(e), according to the models: C = C(NonCo) + C(Co)e(-kH(e) ) for exposed lenses; C = C(NonCo) + C(Co) for non-exposed lenses, and C(d) = C(Co)(e(-kH(e) ) - 1). Parameters for consumable and non-consumable ascorbate were estimated to C(NonCo) = 0.04 and C(Co) = 0.11 micromol/g wet weight of lens. For lens ascorbate difference, tau = 1/k = 0.86 kJ/m(2). A total of 63% of UVB consumable ascorbate has been consumed after only tau = 0.86 kJ/m(2), while MTD(2.3 : 16) = 3.01 kJ/m(2), indicating that ascorbate decrease is in the order of 3.5 times more sensitive to detecting UVR damage in the lens than forward light scattering. The MTD for avoidance of UVB-induced cataract in the 7-week-old albino Sprague Dawley rat was estimated to be 3.01 kJ/m(2). In vivo UVB exposure of the rat eye decreases lens ascorbate content following an exponential decline, and suprathreshold doses cause greater effect than subthreshold doses.

UVR-B induced cataract development in C57 mice

The evolution of the morphological appearance and intensity of light scattering in C57 mice lenses after exposure to ultraviolet radiation type B (UVR-B) was investigated. A total of 80, 6-week-old female C57BL/6 mice were divided into four groups (n=20). One eye in each animal was exposed in vivo to UVR-B in the 300 nm wavelength region (UVR-B-300nm) to a dose of 5kJm−2 for 15min. The radiation output had λmax at 302nm with 5nm [FWHM]. The animals were consecutively sacrificed at 1, 2, 4 and 8 days after the exposure. Macroscopic lens changes were documented using grid- and dark field illumination photography. Light scattering in the exposed and contralateral not exposed lens was measured quantitatively. Morphological lens changes were documented using grid- and dark field illumination photography. In vivo exposure to UVR-B-300nm induced subcapsular cataract in all exposed lenses and occasionally cortical and nuclear cataract at all investigated time points. Exposed lenses scattered light significantly higher on all investigated days compared to contralateral non-exposed lenses. A transient increase of light scattering peaking at day 2 in exposed as well as in contralateral not exposed lenses was identified. Light scattering of the lenses varies with latency time after exposure. A dose of 5kJm−2 UVR-B-300nm induces light scattering in C57 mice lenses. The increase has a transient peak at 2 days after exposure. The variation of light scattering among days 1, 2, 4, and 8 indicates a dynamic change of scattering characteristics in the mouse lens following unilateral in vivo exposure to 5kJm−2 UVR-B-300nm.

Sodium and potassium in the lens after exposure to radiation in the 300 nm wavelength region

The possible change in sodium and potassium concentration in the lens after an in vivo exposure to radiation in the 300 nm wavelength region was investigated. Both lenses from 12 reference rats and from 80 unilaterally exposed rats were examined. The exposed rats were sacrificed in four groups: 6, 24, 72 and 168 h after exposure. The lenticular cation contents were determined using atomic absorption spectrophotometry. In exposed lenses the concentration of sodium increases whereas that of potassium decreases as the time after exposure increases. The rates of concentration change decrease as the time after exposure increases. The increase in sodium precedes the decrease in potassium. Furthermore, a slight increase in the concentration of sodium is registered, as the time after exposure increases, in the non-exposed contralateral lenses. The registered changes are believed to reflect the water balance in the lenses.

Mass alteration in the lens after exposure to radiation in the 300 nm wavelength region.

The purpose of the present investigation was to elucidate whether radiation in the 300 nm wavelength region (300 nm UVR) induces an alteration of lens mass. Lenses from 12 rabbits were incubated in vitro and the relative wet mass gain was recorded sequentially. The wet mas gain, at 30-40 h postictal interval, was greater in lenses exposed to 3.0-6.0 kJ/m2 300 nm UVR than in non-exposed contralaterals. The coefficients of variation were between 6-10% in determinations of wet mass, dry mass, and mass of lens water in Sprague Dawley rat lenses, the variation among animals being the largest source of inprecision. One eye in each of 80 rats was exposed in vivo to 30 kJ/m2 300 nm UVR, and the rats were sacrificed in groups at consecutive postictal intervals. The in vivo exposure of a lens to 300 nm UVR induced a water accumulation after around 24 h and a reduced increase of dry mass, as compared to in the contralateral non-exposed lens.