Studies on the handling of retinotoxic doses of iodate in rabbits.
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-.
D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001082:Aqueous Humor / Q000032:analysis; D002829:Choroid / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism; D005123:Eye / Q000378:metabolism*; D007452:Iodates / Q000097:blood / Q000378:metabolism* / Q000633:toxicity; D007455:Iodine / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008099:Liver / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D011817:Rabbits; D011877:Radionuclide Imaging; D012160:Retina / Q000187:drug effects* / Q000378:metabolism; D013961:Thyroid Gland / Q000378:metabolism
D007452:Iodates; D007457:Iodine Radioisotopes; D007455:Iodine