ABSTRACT
Accumulation of iodate in eye tissues and fluids as a possible explanation of the retinotoxic effect of iodate has been studied by intravenous injection of NaIO3(30 mg/kg), 125IO-3 and 131I- in rabbits. 125IO-3 was determined in fluids and tissue extracts by precipitation with BaCl2 after addition of KIO3. 125IO-3 was rapidly broken down in blood (T 1/2 = 14 min.). 125IO-3 was not present in aqueous humour, vitreous or extracts from retina, choroid + pigmentary epithelium or liver. Concentrations of 125I were comparable in blood, choroid + pigmentary epithelium and liver tissue while in vitreous and aqueous humour low concentrations of 125I were found which, however, increased gradually during 5 hrs after injection to reach levels comparable with blood levels of 125I. Retina had a low concentration of 125I. The ratio 125I/131I (R) in blood decreases during the first 60 min. after injection followed by a slow rise. R in retina, choroid + pigmentary epithelium and liver was the same as in blood at the same time after injection. During the first 80 min. after injection R was higher in vitreous than in blood while it was lower in aqueous humour than in blood. At longer times after injection R was identical in the three fluids. The investigation has been supplemented with whole body scintigraphy of rabbits injected with NaIO3(30 mg/kg) and 131IO-3 or 131I-. The reduction kinetics of IO-3 to I- by some body fluids, tissues, cystein and glutathione was also studied. It is concluded that the retinotoxic effect of iodate is not due to accumulation of IO-3 in eye tissues, but more likely to damage to biochemical mechanisms involved in the reduction of IO-3 to I-.
Subject(s)
Eye/metabolism , Iodates/metabolism , Iodine/metabolism , Liver/metabolism , Retina/drug effects , Adipose Tissue/metabolism , Animals , Aqueous Humor/analysis , Choroid/metabolism , Erythrocytes/metabolism , Iodates/blood , Iodates/toxicity , Iodine Radioisotopes , Muscles/metabolism , Rabbits , Radionuclide Imaging , Retina/metabolism , Thyroid Gland/metabolismABSTRACT
A statistical study of the co-variation of the concentrations of 19 amino acids and related compounds from 21 persons was performed as a factor analysis of Caq/Cpl and of Caq. Six factors explained about 83% of the observed variation. Factor 1 showed a correlation to alpha-amino-N-butyric acid, valine, methionine, isoleucine, leucine, tyrosine and phenylalanine, factor 2 to lysine, histidine, arginine and glutamine (containing serine), factor 3 to taurine and proline, factor 4 to glycine and cystine, factor 5 to urea and factor 6 to glutamic acid. Only alanine and threonine showed a correlation to different factors in the Caq/Cpl- and the Caq-matrix. This correlation of groups of substances to different and independent factors is considered to be an argument in favour of the existence of six transport systems in the ciliary epithelium for the investigated substances.
Subject(s)
Amino Acids/metabolism , Ciliary Body/metabolism , Epithelium/metabolism , Amino Acids/blood , Aqueous Humor/analysis , Biological Transport, Active , Factor Analysis, Statistical , HumansABSTRACT
Irradiation with visible light of human serum albumin in aqueous solution at pH 8, in the presence of catalytic amounts of rose bengal or methylene blue, resulted in random oxidation of the histidine residues in the protein under consumption of one mole O2, and release of somewhat less than one proton, per histidine residue degraded. An increase of light absorption at 250 nm was proportional to the amount of oxygen consumed. Bilirubin bound to the oxidized protein showed an increased light absorption at its maximum, 460 nm, and a decreased binding affinity, indicating a conformational change of the protein on oxidation of histidine residues. This change also resulted in a slight perturbation of tyrosine light absorption, corresponding to a shift of the chromophore to more polar surroundings. Further, a sensitized oligomerization of albumin was observed, independent of oxidation of the histidine residues, and not consuming oxygen. Irradiation of a complex of human serum albumin with one molecule of bound bilirubin, in the absence of a sensitizing dye, resulted in a fast, non-oxygen consuming process whereby the light absorption maximum of the pigment was shifted 4 nm towards longer wavelength and part of the bilirubin was converted to a more polar pigment, bound less firmly to the protein. This was followed by a relatively slow oxidation of the pigment under uptake of one mole O2. Parallel photooxidation of the protein carrier could not be detected. It is considered possible that the fast, anaerobic process is operative in phototherapy of hyperbilirubinemia in the newborn. Serum albumin is probably not oxidized during this treatment.
Subject(s)
Bilirubin , Serum Albumin , Histidine/analysis , Humans , Hydrogen-Ion Concentration , Oxidation-Reduction , Oxygen/blood , Oxygen Consumption , Peroxidases , Photochemistry , Protein Binding , Spectrophotometry, UltravioletABSTRACT
The concentration of 19 amino acids and related compounds was simultaneuosly determined by means of ion exchange chromatography in the aqueous humour (Caq) and blood plasma (Cpl) of 40 patients with various chronic ocular disorders. The physiological aspects will be published elsewhere. It is of interest to note that very few significant differences have been found between the Caq/Cpl ratios for the groups into which the material could be clinically divided. This enables the conclusion to be drawn that determination of Caq/Cpl for amino acids and related compounds are not of diagnostic importance in the chronic ocular disorders which were studied.
