Polyamine system in developing rat eye and an animal model of retinopathy of prematurity

Abstract

l Background: In experimental models of retinopathy of prematurity (ROP), a vasoproliferative disorder of the retina, retinal lesions are usually assessed by morphological examination. However, studies suggest that the polyamine system may be useful in monitoring proliferation processes. For this reason, polyamine concentrations in rat erythrocytes (RBC) and the regulation of polyamine system in rat eyes under the conditions relevant to ROP were investigated. l Methods: Newborn Wistar rats were reared in room air (control) or exposed first to hyperoxia (60% or 80% oxygen, 2 weeks) and then to normoxia (relative hypoxia, 1 or 2 weeks). Blood was collected from orbital vessels at 2 weeks of age and before death. Polyamine system-related enzyme activities were measured in retina and lens with radioassays. Polyamines were quantified by fluorometry after extraction, dansylation and HPLC separation. l Results: Oxygen (80% only) significantly decreased RBC polyamine concentrations, which then markedly increased after rats were transferred for a week to normal air, suggesting retardation of growth processes and compensatory stimulation, respectively. However, polyamine system changes in the rat eye were not so pronounced. Enzyme activities and polyamine concentrations tended to be lower in retina after hyperoxia and were only slightly higher, with the exception of ornithine decarboxylase, after a subsequent 1 week of normoxia. In litters subjected to normoxia for longer periods no changes were found. l Conclusion: The transient and short-lived alteration in polyamine metabolism, especially in the eye, suggests that exposure of newborn rats to high oxygen supplementation followed by normoxia does not necessarily result in marked retinopathy.

Research Progress and Potential Applications of Spermidine in Ocular Diseases

“…Gralek et al supposed that hyperoxia, known to cause retardation of vessel growth, was related to reduced enzyme activity and polyamine levels in newborn rats for the first 2 weeks of life. They exposed newborn rats to hyperoxia for two weeks and then assessed the levels of polyamines (including spermidine) and enzyme activity (such as ODC and SSAT) in the retina and lens: they both decreased [ 131 ]. In another study, Gralek et al tried to establish a murine model of ROP but failed, but a similar significant variation was not found [ 132 ].…”

“…They exposed newborn rats to hyperoxia for two weeks and then assessed the levels of polyamines (including spermidine) and enzyme activity (such as ODC and SSAT) in the retina and lens: they both decreased [ 131 ]. In another study, Gralek et al tried to establish a murine model of ROP but failed, but a similar significant variation was not found [ 132 ].…”