Relationships between Acetone, Cataracts, and Ascorbate in Hairless Guinea Pigs

Abstract

Acetone is one of the most commonly used industrial solvents. Recent literature indicated that in guinea pigs, but not rabbits, acetone is cataractogenic and that elevated acetone exposure is also associated with depressed aqueous ascorbate levels. Other work indicated that aqueous and lens levels of ascorbate are closely linked and that depressed ascorbate status is related to cataract. Taken together, these papers suggested that acetone exposure, depressed ascorbate levels, and cataract are related, possibly causally. While the possibility that acetone is cataractogenic presented a major health concern, it also presented an opportunity to develop a new model of cataract in which hypotheses regarding anticataractogenic effects of ascorbate could be tested. Albino hairless guinea pigs are immunocompetent animals derived from albino Hartley guinea pigs. Animals were fed diets containing low (4.9 mg/day) and high (55 mg/day) levels of ascorbate. This resulted in distinct groups of animals, one with high tissue ascorbate levels and the other with low, but nonscorbutic ascorbate levels. The tissue levels of ascorbate and the relationship between tissue ascorbate levels and dietary intake indicate that with respect to ascorbate uptake, transport, and concentration, these animals are identical to the standard albino Hartley animals. Daily exposure to acetone was extended for 6 months, with a total applied dose of 65 ml. Absorption of the solvent was maximized by the use of hairless animals. Despite exposure of the animals to higher levels of acetone, in no case (n = 20) were cataracts observed over a 2-year period. This is consistent with results using rabbits. The data show that the hairless guinea pig is a fine model for studies in which ascorbate bioavailability is of importance. However, other models to test the cataractogenic potential of acetone and anticataract effects of ascorbate are needed.

Oxidation, antioxidants and cataract formation: a literature review

“…37 Ascorbate inhibits galactose cataract in guinea pigs 38 while depressed ascorbate levels were associated with acetone-induced cataract in guinea pigs. 39,40 Ascorbate reduces heat-induced damage to lens proteins 41 and delays UV-induced damage to lens proteins, 42 although neither of these models can be described as particularly physiologic. In diabetic rats, ascorbate reduces crystallin leakage from lenses undergoing cataractogenesis.…”

“…Correlation of lenticular concentrations of ascorbate with levels in the diet show that oral intake of ascorbate is crucial in giving adequate levels of the vitamin in the lens, both in guinea pigs 36 and in rats 37 . Ascorbate inhibits galactose cataract in guinea pigs 38 while depressed ascorbate levels were associated with acetone‐induced cataract in guinea pigs 39,40 . Ascorbate reduces heat‐induced damage to lens proteins 41 and delays UV‐induced damage to lens proteins, 42 although neither of these models can be described as particularly physiologic.…”

Estudo comparativo do estresse oxidativo após facoemulsificação experimental com e sem implante de lentes intra-oculares em cães

“…Entretanto, seu papel fundamental é como cofator de várias enzimas em diferentes vias metabólicas, como, por exemplo, da GPx.Participa de diversos processos de detoxificação, como a remoção de peróxidos via GPx. Por outro lado, a geração de grandes quantidades de peróxido de hidrogênio pelas células pode promover um acúmulo de GSSG, gerando radical superóxido ( O 2 agentes oxidantes identificados nos olhos de animais de vida diurna incluem oxigênio singlete, peróxido de hidrogênio, radical ânion superóxido, radical hidroxila, riboflavina e triptofano(TAYLOR et al, 1993). Os principais cátions são sódio, potássio, cálcio e magnésio.…”