Human Vitreous Humor Research Articles

Analysis of human vitreous humor with two-dimensional gel electrophoresis

目的 优化并确立一套适合人眼玻璃体的双向电泳实验方法.方法 收集14只健康捐献眼的玻璃体,提取玻璃体总蛋白,改进条件以确立玻璃体蛋白质的双向电泳(2-DE)技术流程.结果 以IPG胶条(pH 4～7,线性,L)进行一向等电聚焦,以12%SDS均匀胶进行二向垂直电泳,获得人玻璃体分布均匀的双向凝胶电泳图谱并分离出400多个蛋白点,凝胶图谱的重复性较好.结论 该优化的技术流程能有效提取及分离玻璃体蛋白质,为进一步的差异蛋白质组研究奠定基础。

Penetration of 1% voriconazole eye drops into human vitreous humour: a prospective, open-label study

Although there have been reports describing the use of 1% voriconazole eye drops in the treatment of fungal infections, little is known about the penetration of voriconazole eye drops into the vitreous humour. The aim of this study was to elucidate if topical application of 1% voriconazole eye drops could reach therapeutic levels in the vitreous humour. A prospective, open-label trial involving 10 participants selected from patients scheduled to undergo elective, posterior segment surgery. Participants received 1% voriconazole solution, preserved with 0.01% benzalkonium chloride, hourly for four doses or four times a day for 3 days. Vitreous humour was obtained at the start of surgery and analysed using a validated high-performance liquid chromatography assay. The minimum and maximum voriconazole concentration after hourly dosing (n = 5) was 0.1 and 1.1 microg/mL, respectively, whereas the median was 0.3 microg/mL. Samples were taken between 0.8 and 5.4 h after the last dose, with the median at 1.2 h. Almost all voriconazole concentrations from the four times a day group (n = 5) were below the limit of quantification. One per cent voriconazole eye drops are able to penetrate into human vitreous humour. Adequate concentration for treatment of sensitive Candida species can be achieved upon hourly administration.

Analysis of age-related carbonylation of human vitreous humor proteins as a tool for forensic diagnosis

Age-related changes of protein carbonylation due to oxidative damage in human vitreous humors were analyzed. The vitreous samples were collected from 51 autopsied bodies (male: 27, 13–87 years-old, female: 24, 18–80 years-old) whose postmortem interval was less than 4 days. Total protein carbonyl content was assessed by colorimetry using 2,4-dinitrophenylhydrazine and particular carbonylated proteins were identified by immunostaining of vitreous proteins resolved by SDS–PAGE and MALDI-TOF MS with peptide mass fingerprinting. No significant correlation was found between total protein carbonyl content and biological age. However, two major proteins, albumin and transferrin, were found to be heavily carbonylated in the samples from individuals age 40 or over. Furthermore, an immunostained cluster of proteins at 50–60 kDa was discernible in the samples of aged individuals, and it was revealed to contain alpha enolase, pigment epithelial differentiating factor, type 2 keratin subunit protein, and S-arrestin. The results of this study suggest that some retinal proteins detected in the vitreous humor sample would be markers of age-related oxidative stress and biological age.

Determination of ofloxacin and moxifloxacin and their penetration in human aqueous and vitreous humor by using high-performance liquid chromatography fluorescence detection

Information on comparing the penetration of ofloxacin and moxifloxacin in the human eye is unavailable, although these two antibiotics are commonly used in ophthalmic surgery. There is a need for a rapid, reliable, and sensitive methodology for their determination in ocular fluids. We developed a robust HPLC procedure with fluorescence detection for simultaneous analysis of ofloxacin and moxifloxacin in human and rabbit aqueous and vitreous samples. The linearity of the method ranged from 10 ng/ml to 100 μg/ml with r 2 > 0.996. Most inter- and intrabatch imprecision was about 5% (range 1.6–7.6%), recoveries between 95 and 104%, and accuracies between 93 and 104% at 0.1 and 1 μg/ml. The detection limits of both compounds were 10 ng/ml (0.028 nmol/ml for ofloxacin and 0.023 nmol/ml for moxifloxacin). No sample treatment was necessary for aqueous humor and only acetonitrile precipitation was required for vitreous humor. The chromatographic time was short, 22 min. We applied this method to study penetrations of ofloxacin and moxifloxacin in aqueous and vitreous humors of human and rabbits. There was no significant difference of penetration between the two antibiotics into aqueous and vitreous but ofloxacin was found at significantly higher concentrations in aqueous than in vitreous. We also detected contralateral transfer of the antibiotics in rabbit eyes.

GC-FID determination of cocaine and its metabolites in human bile and vitreous humor

Gas chromatography was used in combination with flame ionization detection (GC-FID) to develop a method for determining cocaine and its two metabolites, benzoylecgonine (BEG) and ecgonine methyl ester (EME), in bile and vitreous humor. The method used a 12 m x 0.2 mm i.d. column of 0.33 microm film thickness packed with 5% phenylmethylsiloxane, and proadifen as a reference compound. Drug-free bile and vitreous humor samples were used to prepare solutions of the target compounds at concentrations over the range 0.1-4 microg ml(-1) that were subjected to solid-phase extraction through Bond Elut Certify columns and derivatized with 99:1 (v/v) N,O-bis-trimethylsilyltrifluoroacetamide (BSTFA)/trimethylchlorosilane (TMCS). Calibration graphs were highly linear, with correlation coefficients above 0.99 in all instances. Also, the precision of the method was found to be quite acceptable, with coefficients of variation less than 5% for bile and less than 7% for vitreous humor. The average extraction yields ranged from 73.6% to 91.2% for bile and from 71.5% to 92.2% for vitreous humor. The proposed method was used to analyse 26 samples of bile and as many of vitreous humor from individuals fatally poisoned by cocaine, whether alone or in combination with other drugs. The mean drug levels found were 0.75 and 1.54 microg ml(-1) for cocaine in bile and vitreous humor, respectively, 6.35 and 0.94 microg ml(-1) for BEG, and 2.18 and 0.61 microg ml(-1) for EME.

Alterations in human vitreous humour following cataract extraction

Cataract extraction is associated with the risk of posterior vitreous detachment, macular edema and retinal detachment possibly as a result of a disturbance to the vitreous body during surgery. While it is common for lens cortical fiber debris to leak into the vitreous humour during cataract extraction, the extent to which the vitreous humour is altered post-surgery is unknown. The current study examines the integrity of the vitreous humour of pseudophakic and phakic human donor eyes by comparing the proteome, the viscosity and the size distribution of macromolecules in different regions of the vitreous humour from human pseudophakic and phakic donor eyes. Major differences between the proteomes of anterior and posterior vitreous humour were observed in phakic and pseudophakic donor eyes. Seventeen spots identified as complete, modified or cleaved forms of αA-, αB-, βA 4-, βB 2, and γS-crystallins were present in the anterior vitreous humour of all pseudophakic eyes studied. Crystallins were not detected in the posterior vitreous humour of the pseudophakic eye or the vitreous humour of the phakic eye. Significant alterations in abundance and/or modification of transthyretin, alpha antitrypsin, and retinoic acid binding protein were observed in all locations of pseudophakic vitreous humour as compared to phakic samples. In addition, a significant decrease in the number and intensity of protein spots was observed for the posterior vitreous humour of pseudophakic eyes when compared to posterior vitreous humour of phakic eyes. Proteins which were affected include antioxidant proteins and enzymes such as carbonic anhydrase and trisephosphate isomerase. A reversal of the viscosity gradient, anterior to posterior, in the vitreous humour of pseudophakic eyes was observed concomitant with alterations in the distribution of 50 nm particles. These particles are likely primarily composed of hyaluronan. While varying degrees of vitreous degradation may have existed prior to surgery and may have contributed to the cataract formation, in no case did the phakic donor eyes exhibit the same alterations in the vitreous humour proteome, viscosity or particle sizes as did the pseudophakic donor eyes. The examination of phakic/pseudophakic donor eye pairs confirmed that the vitreous humour proteome and structural integrity were very similar in the matched phakic donor eye to eyes from donors with no history of cataract. Even though the number of samples for this study was limited, the observed changes support the hypothesis that alterations in the vitreous humour proteome occur in psuedophakic eyes with concurrent alterations in the structure of the vitreous humor. These modifications of the microenvironment of the retina may contribute to the development of retinal complications following cataract surgery.

Measurement of activities in two different angiotensin II generating systems, chymase and angiotensin-converting enzyme, in the vitreous fluid of vitreoretinal diseases: A possible involvement of chymase in the pathogenesis of macular hole patients

Purpose. To investigate possible involvement of chymase and angiotensin-converting enzyme (ACE) in the pathogenesis of vitreoretinal diseases, both of which are related to the production of angiotensin II. Methods. We measured chymase and ACE activities in the vitreous in the 54 affected eyes of 54 patients who had undergone vitreous surgery for idiopathic macular holes (MH, n = 14), proliferative diabetic retinopathy (PDR, n = 14), idiopathic epiretinal membranes (ERM, n = 13), and rhegmatogenous retinal detachment (RRD, n = 13). Results. Chymase activities in the vitreous from patients with MH, PDR, ERM, and RRD were 1.87 ± 0.53, 0.06 ± 0.04, 0.40 ± 0.12, and 0.08 ± 0.03 (mean ± SE) mU/mg protein, respectively, and ACE activities in the vitreous humor were 0.18 ± 0.09, 0.30 ± 0.07, 0.01 ± 0.01, and 0.03 ± 0.02 (mean ± SE) mU/mg protein, respectively. Chymase activity was significantly elevated in MH among these diseases (p < 0.01, Scheffe), and ACE was significantly activated in PDR compared to ERM and RRD (p < 0.05, Scheffe). Conclusions. Our results suggest that two different angiotensin II generating systems are activated in human vitreous humor; an increased activity of chymase may play a possible role in the formation of macular holes.

Catalogue of soluble proteins in human vitreous humor by one-dimensional sodium dodecyl sulfate–polyacrylamide gel electrophoresis and electrospray ionization mass spectrometry including seven angiogenesis-regulating factors

A catalogue of proteins in the human vitreous humor may contribute to elucidating the pathogenesis of various diseases in ophthalmology. To improve the recovery of proteins in vitreous, we applied one-dimensional sodium dodecyl sulfate–polyacrylamide gel electrophoresis (1D-PAGE). Proteins were extracted from unstained gel strips and digested in gel with trypsin and the peptides were analyzed by capillary-column reversed-phase high-performance liquid chromatography coupled with electrospray ionization-ion trap-mass spectrometry. From a patient with diabetic retinopathy, 84 different proteins were identified. Most of the proteins which we identified in vitreous previously using 2D-PAGE were also identified in the present study. In total, we identified 121 different proteins including five proteins seen at the genomic level only. Four angiogenic factors, insulin-like growth factor, vascular endothelial growth factor, fibroblast growth factor, and placental endothelial cell growth factor, and three anti-angiogenic factors, pigment epithelium-derived factor, endostatin, and thrombospondin, were found, and this may contribute to elucidating the pathological changes in the concentration and the modified structures of these proteins, in diseases of the retina, especially, diabetic retinopathy.

Catalogue of soluble proteins in the human vitreous humor: comparison between diabetic retinopathy and macular hole

Two-dimensional gel electrophoresis and mass spectrometry were used to make a catalogue of soluble proteins in the human vitreous humor (VH). Fifty-one different proteins were identified on silver-stained two-dimensional (2D) gel patterns with VH proteins obtained from diabetic retinopathy and macular hole. Thirty of these have not been listed in the reported 2D profiles of plasma. Immunoglobulin (Ig), α1-antitrypsin, α2-HS glycoprotein,and complement C 4 fragment showed stronger spots in VH with diabetic retinopathy patient samples than those with macular hole. Pigment epithelium-derived factor, a potent inhibitor of angiogenesis in the cornea and vitreous, was clearly detected in VH with diabetes. It is impressive that the inhibitor increases in the vitreous with proliferative angiogenesis.

Capillary zone electrophoresis and artificial neural networks for estimation of the post-mortem interval (PMI) using electrolytes measurements in human vitreous humour.

Determination of electrolyte concentrations (mainly potassium) in vitreous humour has long been considered an important tool in human death investigations for the estimation of the post-mortem interval (PMI). On the basis of its well known potential in ion analysis, capillary zone electrophoresis (CZE) has recently been applied to achieve a rapid and simultaneous determination of inorganic ions in this extracellular fluid. In the present work, artificial neural networks (ANN) were applied for modelling of the relationship of multicomponent CZE analysis of K+, NH4+, Na+, and Ba2+ ions in vitreous humour with PMI. In a study based on 61 cases with different causes of death and a known PMI ranging from 3 to 144 h, the use of ANNs considering all inorganic ion data from the human vitreous humour, achieved a substantial improvement of post-mortem interval prediction. Good linear correlation was observed (r2 = 0.98) and in comparison to the traditional linear least squares (LLS) method applied only to K+ levels in the vitreous humour, the prediction of PMI with ANN was improved by a factor of 5 from approximately +/- 15 h to less than 3 h.

Biochemical Analysis of Arginase and Ornithine Carbamoyltransferase in Human Vitreous Humor

Background The presence of arginase and ornithine carbamoyltransferase (OTC'ase) enzymes in human vitreous humor after death was investigated in this study. To the best of our knowledge, there is no prior report on the activity of arginase or ornithine carbamoyltransferase in human vitreous humor. Methods The presence of arginase and OTC'ase activities were examined in the human vitreous humor of 19 samples. Spectrophotometric methods were used to determine activities of arginase and OTC'ase. Results Arginase activity was detected in human vitreous humor, whereas OTC'ase activity was below the detection limit. Therefore, we focused on biochemical analysis of arginase in human vitreous humor. Kinetic properties of arginase activity in vitreous humor were optimized. In contrast to other arginases, optimal preincubation temperature and pH were 40°C and 8.8, respectively. Km of vitreous arginase for L-arginine was 6 mM. Preincubation of the enzyme with Mn 2+ ions caused a significant increase (33%) in arginase activity. Conclusions The activity and presence of arginase as well as its kinetics in human vitreous are documented in this study. Biochemical functions and the importance of arginase in vitreous humor are not well understood. However, its presence may be explained by means of its involvement in polyamine biosynthesis as observed in the other extrahepatic tissues.

The relevance of intraoperative microbial contamination and of native human vitreous humor in the developement of postoperative infections

Hintergrund Akute postoperative infektiose Endophthalmiden stellen eine der am meisten gefurchteten Komplikationen nach intraokularen Eingriffen dar. Fur deren Entwicklung ist die intraokulare Keimvermehrung und Keimausbreitung essentiell. Entsprechend den Ergebnissen alterer Untersuchungen stellt Vitreus ein gutes Nahrmedium dar, deshalb musste auch bereits ein kleines Inokulum zu einer manifesten Endophthalmitis fuhren. Der Zweck unserer Untersuchungen bestand in der Klarung der Fragestellungen ob und wenn ja welche Keime nach Cataractopcration bzw. Pars plana Vitrektomie im Augeninneren verbleiben, und ob nicht infiammierter menschlicher Glaskorper tatsachlich ein gutes, die Keimvermehrung forderndes Medium darstellt.

Capillary zone electrophoresis of potassium in human vitreous humour: validation of a new method

The analysis of potassium in the vitreous humour has long been regarded as an important tool in medicolegal and forensic toxicological investigation, particularly for the determination of the post-mortem interval. The present work was aimed at the optimisation and validation of a reliable, simple and fast capillary electrophoresis method for potassium analysis in the human vitreous humour with indirect UV detection at a wavelength of 214 nm. Electrophoretic separations were carried out in a running buffer comprising 5 m M imidazole, 5 m M 18-crown-6 ether and 6 m M d,l α-hydroxybutyric acid (HIBA), adjusted to pH 4.5. Constant voltage runs were carried out by applying a voltage of 500 V/cm at 25°C. The samples were injected in the hydrodynamic mode at the anodic end of the capillary (0.5 p.s.i. for 10 s; 1 p.s.i.=6894.76 Pa). The method showed good linearity in the concentration range from 6.5 m M to 16.25 μ M, with an r 2value of 0.9994. The limit of detection, based on a signal-to-noise ratio of three, was 9.0 μ M. Absolute intra-day RSDs of migration times were <0.40%, while the day-to-day values were ⩽1.72%. Absolute peak area reproducibility was always better than 2.50%. A comparison of capillary electrophoresis with flame photometry on twelve real autopsy samples showed an excellent correlation with an r 2 value of 0.9333. A preliminary application to real cases (20 subjects) was carried out plotting vitreous humour potassium vs. post-mortem interval with a resulting r 2 of 0.904 and a Y-intercept of 4.75 m M, in agreement with the existing literature.

Capillary ion analysis of potassium concentrations in human vitreous humor.

Capillary ion analysis (CIA) is a form of capillary electrophoresis which uses the differential electrophoretic mobility of ions to perform a separation of an ionic mixture. Application of this technique for direct detection of potassium concentrations in human vitreous humor was the purpose of this investigation. CIA was performed using a Waters Quanta 4000 Capillary Electrophoresis System with a 745 Data Module using a 75 microm x 60 cm capillary and a run electrolyte of 67.7 mg hydroxyisobutyric acid (HIBA), 52.8 mg 18-crown-6-ether and 64 microL UV-CAT-1 reagent (4-ethylbenzylamine) in a volume of 100 mL water (18 Mohm) with a voltage of 20 kV using ultraviolet absorption detection at 214 nm. Migration times were: ammonium ion, 2.86 min; potassium, 3.24 min; calcium, 3.84 min; sodium, 3.98 min; barium (internal standard), 4.68 min; and lithium, 4.79 min. Correlation coefficients (r) between peak area ratios and concentration ranges of 2.5-144 mmole/L (100-1000 ppm) were from 0.9855 to 0.9999. Coefficients of variation (CV) ranged from 1.45 to 13.8% between days and from 1.38 to 9.43% within-day. Application of this methodology to twenty-five vitreous humor specimens from forensic cases was compared to analysis by ion-specific electrode for potassium concentration. Comparison of CIA to ion-specific electrode analysis of vitreous humor potassium concentrations revealed a correlation coefficient of 0.9642. CIA is applicable to forensic analysis of potassium concentration in forensic vitreous humor specimens. Quantitation of numerous cation concentrations is possible by direct CIA of vitreous humor.

Bacterial Growth in Human Vitreous Humor

The aim of this study was to investigate the capacity of human vitreous to support bacterial growth and to show differences in the growth kinetics of gram-positive and gram-negative bacteria. Vitreous gel of 70 keratoplasty donor eyes was sampled under sterile conditions, screened microscopically for cellular components and tested for sterility and levels of antibiotic drugs by bio-assay. The samples were inoculated with clinical isolates ofPseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus viridansandStreptococcus pyogenes.As control each strain was added both to 0.9% sodium chloride solution and to Mueller-Hinton broth. In order to determine bacterial growth the number of colony forming units was determined 4, 6, 24, 48 and 72 hr after inoculation by viable count. Vitreous gel did not support bacterial growth; the tested strains could not be recovered after 48 hr. Similar results could be obtained with sodium chloride; whereas in Mueller Hinton broth the strains showed normal pattern of growth. It seems that vitreous humor has inherent antibacterial capacity in vitro, although the responsible factors remain unknown.

Determination of ascorbic acid in human vitreous humor by high-performance liquid chromatography with UV detection

PURPOSE. Ascorbic acid (AA) accumulates in vitreous at a concentration several times higher than in plasma. It has been suggested that AA may serve as an antioxidant that protects ocular tissues from free radical attack. There are many reports about the concentration of AA in ocular tissues. However, AA in adult human vitreous humor has not been determined. We measured concentrations of AA from pathologic human vitreous samples and compared the results. METHODS. AA was measured by high-performance liquid chromatography (HPLC) with UV detection. Human vitreous humor was collected from patients undergoing pars plana vitrectomy. RESULTS. AA was quantified in vitreous humor of proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), macular hole (MH), idiopathic premacular fibrosis (PMF), and Terson syndrome (Terson). The concentrations of AA were 120.9 ± 36.3 mg/ml (mean ± SD), 129.8 ± 36.6, 311.5 ± 126.7, 446.9 ± 154.2 and 406.0 ± 22.0, respectively. There was no significant difference between the PDR and the PVR groups (unpaired t-test). Patients with PDR and PVR showed significantly lower concentrations of AA than those with MH, PMF, and Terson (p < 0.01). CONCLUSIONS. These findings suggest that increased oxidative stress may be produced in the ocular tissues of eyes with PDR and PVR, and AA appears to be consumed (oxidized) in performing its protective role.

Cathepsin A activity of normal bovine ocular tissues and pathological human intraocular fluids.

Cathepsin A activity assayed with N-Cbz-Phe-Ala, N-Cbz-Glu-Tyr and N-Cbz-Glu-Phe as substrates, was measured in fresh corneas, lenses, aqueous humor, vitreous humor and choroid plus retinal pigment epithelium taken from normal bovine eye balls and in human intraocular fluids from the eye balls in various ocular diseases (cataract, glaucoma, diabetes, intraocular tumors). Cathepsin A exhibited a pH optimum at 5.0 and showed the highest specificity towards N-Cbz-Phe-Ala as a substrate. In bovine ocular tissues high cathepsin A activity was found in the choroid plus retinal pigment epithelium and in cornea. The lens and the vitreous humor showed low enzyme activity and the aqueous humor none at all. In the human aqueous humor of the eye with cataract cathepsin A activity was more than three times higher then in the eye with choroid tumor. In human vitreous humor in absolute glaucoma the activity was twice as high as in melanoma and almost three times higher than in the case of lung metastatic tumor. Diabetes in glaucoma increased seven fold cathepsin A activity in the vitreous humor.

Nonlinear refraction in vitreous humor

We extend the application of the z-scan technique to determine the nonlinear refractive index (n(2)) for human and rabbit vitreous humor, water, and physiological saline. In these measurements there were nonlinear contributions to the measured signal from the aqueous samples and the quartz cell that held the sample. Measurements were made with 60-ps pulses at 532 nm. To our knowledge, this is the first measurement of the nonlinear refractive properties of biological material.

Monoclonal Antibodies Against Two Epitopes in the Human α1(IX) Collagen Chain

Type IX collagen is a component of cartilage and vitreous humor. Its structure and matrix localization suggest it may serve to mediate interactions between fibrillar collagen, proteoglycan and other matrix components. Consequently, abnormalities in type IX collagen may result in chondrodysplasia. In this paper we describe the preparation and use of two monoclonal antibodies which recognize peptide sequences within the human cartilage α1(IX) collagen chain. Antibody 23-5D1 is highly sensitive and highly specific. It permits the immunoblot detection of type IX collagen extracted from milligram amounts of normal and chondrodysplastic cartilage; it also identifies the “short” form of the α1(IX) chain in human vitreous humor. Antibody 37-10H7 is highly specific, but of low sensitivity. It was used to make the new observation that an N-linked oligosaccharide is present in the amino-terminal globular domain of the a1(IX) chain. We anticipate that these antibodies may be valuable tools in the study of human and other mammalian chondrodysplasias.

UV Filters in Human Lenses: Tryptophan Catabolism

Primate lenses are unique in that they convert tryptophan (trp) into 3-hydroxykynurenine glucoside (30HKG). This is the major short-wave absorbing pigment present in human lenses and it may play a role in protecting the eye from UV-induced photodamage. A study has been performed on aspects of this metabolic pathway in human lenses. A significant rate of synthesis could be observed in a 24-hr period using intact lenses to which radiolabelled tryptophan had been added. Label was found in kynurenine (Kyn), 3-hydroxykynurenine (30HKyn) and 30HKG, although always to the greatest extent in the latter metabolite. Considerable variation in the proportion of label incorporated into 30HKG was observed. Older lenses tended to accumulate a greater percentage into the glucoside; the data indicating a generally greater flux throught the trp catabolic pathway in lenses above 60 years of age. Pulse-chase experiments on lens pairs suggested that there may be a significant loss or metabolism of 30HKG. Biosynthesis of 30HKG was found to take place in the lens epithelial cells. A linear rate of 30HKG efflux from organ cultured lenses was observed indicating that one pathway for removal of this compound involves diffusion through the lens capsule. That this pathway also occurs in vivo was confirmed by analysing samples of human vitreous humour. Based on efflux rates from cultured lenses (1·07 × 10 -3 ± 0·293 × 10 -3 ümol hr -1 n = 5), half-life values for 30HKG in the lens ranging between 7 and 40 hr were calculated. Since the concentration of 30HKG was found to be constant throughout the lens, a model is proposed in which the UV filter substance is synthesized in the epithelial zone, diffuses freely through the lens body and effluxes from the lens into the vitreous. This efflux appears to be the major route for removal of 30HKG from the lens. A marked age-related decrease in the lenticular level of 30HKG was observed. This was closely correlated with a drop in the level of 3-hydroxykynurenine, indicating that the decrease in concentration of the major human lens UV filter compound with age is not due to an alteration in glucosylation but may be the result of a fundamental change in lenticular trp catabolism with age.