Microplate assay of ascorbic acid in aqueous humor with bicinchoninic acid

An Assessment of Cataract Severity Based on Antioxidant Status and Ascorbic Acid Levels in Aqueous Humor

Cataract is the leading cause of blindness throughout the world. Currently, the cataract severity evaluation is based on the subjective LOCS III guideline. To ameliorate the evaluation system and develop an objective and quantitative analysis, we investigated the relationships among aqueous humor total antioxidant capacity (AqTAC), ascorbic acid (AqAA) concentration, and cataract severity. In this study, we enrolled 130 cataract patients who underwent phacoemulsification between April 2019 and March 2020. The AqTAC and AqAA were measured by our own developed TAC assay and commercially available kit. Cataract severity was recorded by nuclear opalescence (NO) and cortical cataract (CC) degree according to LOCS III. Cumulative dissipated energy (CDE) during phacoemulsification was recorded to verify the severity of the cataract. As a result, we found a moderate correlation between AqTAC and CDE (p < 0.001). In addition, we found AqTAC independently associated with the CDE when analyzed by multivariate linear regression (p < 0.001). AqTAC also negatively correlated to cataract severity when measured by NO and CC (p = 0.012 in NO grade 3 vs. grade 1; p = 0.012 in CC grade 2 vs. grade 1; p < 0.001 in CC grade 3 vs. grade 1). We further found AqAA provided 71.9 ± 13.5% of AqTAC, and showed a high correlation (rho = 0.79, p < 0.001). In conclusion, we found a significant correlation between AqTAC/AqAA and cataract severity measured by CDE. The correlation was superior to the correlation between LOCS III and CDE. Aqueous humor TAC owns the potential to assess cataracts in an objective and quantitative way.

An evaluation of protein assays for quantitative determination of drugs

We have evaluated the response of six protein assays [the biuret, Lowry, bicinchoninic acid (BCA), Coomassie Brilliant Blue (CBB), Pyrogallol Red-Molybdate (PRM), and benzethonium chloride (BEC)] to 21 pharmaceutical drugs. The drugs evaluated were analgesics (acetaminophen, aspirin, codeine, methadone, morphine and pethidine), antibiotics (amoxicillin, ampicillin, gentamicin, neomycin, penicillin G and vancomycin), antipsychotics (chlorpromazine, fluphenazine, prochlorperazine, promazine and thioridazine) and water-soluble vitamins (ascorbic acid, niacinamide, pantothenic acid and pyridoxine). The biuret, Lowry and BCA assays responded strongly to most of the drugs tested. The PRM assay gave a sensitive response to the aminoglycoside antibiotics (gentamicin and neomycin) and the antipsychotic drugs. In contrast, the CBB assay showed little response to the aminoglycosides and gave a relatively poor response with the antipsychotics. The BEC assay did not respond significantly to the drugs tested. The response of the protein assays to the drugs was further evaluated by investigating the linearity of the response and the combined response of drug plus protein. The results are discussed with reference to drug interference in protein assays and the development of new methods for the quantification of drugs in protein-free solution.

8-Isoprostaglandin F2a and ascorbic acid concentration in the aqueous humour of patients with exfoliation syndrome

BACKGROUND/AIMS

The authors investigated the concentrations of 8-isoprostaglandin F(2a), a marker of oxidative stress in vivo, and ascorbic acid, a protectant against oxidative damage, in the aqueous humour of patients with exfoliation syndrome (XFS) and cataract and compared the results with those in age matched patients with cataract, but without XFS, to determine whether XFS is associated with increased oxidative stress.

METHODS

Aqueous humour was aspirated at the beginning of phacoemulsification cataract surgery from 27 eyes of 27 cataract patients with XFS and 27 eyes of 27 age matched cataract patients without XFS. 8-Isoprostaglandin F(2a)concentration in the aqueous was determined with a commercial immunoassay; ascorbic acid concentration was measured with a microplate assay method.

RESULTS

The mean concentration of 8-isoprostaglandin F(2a)in the aqueous from patients with XFS (2429 (SD 2940) pg/ml; range 400-10500 pg/ml) was significantly higher than that measured in the aqueous of age matched control patients (529.1 (226.8) pg/ml; range 325-1000 pg/ml); (p = 0.0028). Furthermore, mean ascorbic acid concentration in XFS patients (0.75 (0.39) mM; range 0.28-1.70 mM) was significantly lower than that found in control patients (1.19 (0.47) mM; range 0.53-2.4 mM); (p = 0.0005). There was a reverse correlation between 8-isoprostaglandin F(2a)and ascorbic acid concentration.

CONCLUSION

8-Isoprostaglandin F(2a)was significantly increased in the aqueous of patients with XFS, and ascorbic acid was decreased, providing evidence of a role for free radical induced oxidative damage in the pathobiology of XFS.

Ascorbic acid concentration is reduced in the aqueous humor of patients with exfoliation syndrome

PURPOSE

To investigate whether there is a role for ascorbic acid in the development of exfoliation syndrome (XFS).

DESIGN

A case-control study was undertaken that included consecutive patients with and without XFS in whom cataract surgery was indicated. Patients with ophthalmic conditions other than XFS and conditions that may influence ascorbic acid levels were excluded.

METHODS

A prospective institutional study was undertaken. A small volume of aqueous humor was aspirated at the beginning of phacoemulsification cataract surgery. Eighty aqueous samples, 40 samples from 40 eyes of 40 cataract patients with XFS and 40 samples from 40 eyes of 40 age matched cataract patients without XFS, were collected and analyzed. Ascorbic acid concentration was evaluated in the aqueous samples with a microplate assay method.

RESULTS

The mean +/- SD concentration of ascorbic acid in the aqueous from patients with XFS (0.86 +/- 0.43 mM; range, 0.12 to 1.7 mM) was significantly lower than the concentration of ascorbic acid found in the aqueous of age-matched control patients (1.15 +/- 0.50 mM; range 0.42 to 3.1 mM; P =.0068). Total mean protein concentration was found to be significantly higher in the XFS group (481.1 +/- 196.8 pg/dl versus 336.3 +/- 86.4 pg/dl in the controls; P <.0001). Nevertheless, no correlation could be established between ascorbic level and protein concentration.

CONCLUSIONS

A significantly reduced mean level of ascorbic acid was observed in the aqueous humor of patients with XFS. In view of the fact that ascorbic acid is a major protective factor against free radical action, a role for free radical action is possible in the pathobiology of XFS.