ROZMAN, R.; MENON, J.M.*; William Paterson University, New Jersey; William Paterson University, New Jersey: Effects of retinol and phytol on oxidative stress during anuran metamorphosis and regeneration.
Retinoic acid, a metabolite of retinol (vitamin A) is a common teratogen causing several embryonic malformations and changes in pattern formation in amphibians. The diverse activities of retinoids are primarily mediated by retinoid receptors, the retinoic acid receptors (RARs) and retinoid X receptors (RXRs). Retinol is known to induce oxidative stress during tail regeneration in tadpoles and additionally, reactive oxygen species are known to influence gene expression and signal transduction pathways. The objectives of this study were to determine a) the effect of retinol alone and in combination with phytol (whose metabolits, phytanic acid is an RXR selective ligand) on metamorphosis and tail regeneration in Xenopus laevis tadpoles and b) whether retinol and/or phytol modulates oxidative stress via gene expression of antioxidant enzymes superoxide dismutase (SOD) and catalase. Tadpoles treated with phytol alone showed increased growth and rate of metamorphosis among all the groups. Tadpoles when treated with both retinol and phytol together showed better survival and rate of growth compared to retinol alone (the least growth). Several retinol related limb malformations were observed in retinol treated and retinol + phytol groups. Rate of tail regeneration following amputation was as follows: phytol treated group > control > retinol + phytol > retinol. RT-PCR analysis showed that retinol treatment downregulated gene expression for SOD and catalase, indicating increased oxidative stress. In conclusion a) in addition to well known teratogenic effect, retinol may also induce oxidative stress and influence morphogenetic processes and b) phytol or phytanic acid reduces retinol induced oxidative stress by probably enhancing antioxidant defenses.