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D.T. Organisciak, K.M. Henkels, L.S. Barsalou, R.M. Darrow; Hyperthermic Treatment Alters Rat Rod Outer Segment Crystallin Levels . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5146.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the presence and expression levels of crystallins in rat retinas and ROS in response to hyperthermia. Methods: Weanling male Sprague–Dawley rats were reared in either dim cyclic light or in darkness. At P60, animals were dark–adapted and then treated in darkness under euthermic or hyperthermic conditions for 1–4 hours. Core body temperatures were 37.2oC and 39.7oC, respectively, for the untreated and heat–treated animals. For each time point, ROS were isolated from 2 separate groups of 4 cyclic– or dark–reared animals. ROS proteins were separated and visualized on 2D–gels, while crystallins were identified by western analysis with individual or class specific antibodies. For gene profiles analyzed via real–time PCR, retinas were excised from groups of three animals either cyclic– or dark–reared. Individual comparisons of genes in hyperthermic samples were made to the gene expression profile of euthermic rat retinal samples taken at the start of the experimental period. Results: Hyperthermic treatment for 2 hours in darkness resulted in a significant reduction in ROS crystallin immunoreactivities of both cyclic– and dark–reared rats when compared to euthermic animals. Following 4 hours of hyperthermia, ROS crystallin immunoreactivities returned to euthermic levels. The expression of individual crystallin genes in rat retinas were modestly changed by hyperthermia. In dark–reared rats, γ crystallins were lower after 4 hours of hyperthermia. Although ß crystallin levels were higher after 2 hours, the expression levels of these crystallins were also lower following 4 hours of hyperthermia. In cyclic light–reared rats, ßA3/A1 crystallin expression levels were 5–fold lower after 4 hours of hyperthermia. αA crystallin gene expression was largely unaffected by hyperthermia in both types of rats, while αB crystallin expression was elevated. Conclusions: Hyperthermia leads to a marked reduction in ROS crystallins for 2 hours, followed by a reintroduction of crystallins after 4 hours. The reintroduction of ROS crystallins does not appear to result from dramatic increases in gene expression in either cyclic light– or dark–reared rats. This data suggest that endogenous crystallins may move into or out of the ROS during hyperthermic treatment.
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