Abstract

Vitamin A is essential for the maintenance of normal epithelium, glandular and immune function, development and metamorphosis in amphibians. Over-supplementation, however, can be detrimental, affecting the hepatobiliary, reproductive and skeletal systems in mammals and birds and the integumentary system of reptiles. The results of experimental vitamin A supplementation in a captive population of African foam-nesting frogs (Chiromantis xerampelina) known to be vitamin A deficient were previously reported.¹ The current study investigates the histopathology of these experimentally supplemented animals, with an emphasis on lesions attributable to vitamin A-induced toxicity and those associated with hypovitaminosis A post-treatment. Experimental supplementation consisted of a control group receiving a diet containing 342,000 IU/kg of vitamin A and three treatment groups consisting of: 1) increased dietary vitamin A (822,510 IU/kg), 2) topical administration of approximately 50 IU of vitamin A palmitate every other day, and 3) topical administration of approximately 50 IU of vitamin A palmitate once weekly. Both of the groups given topical vitamin A were also fed the control diet. Histopathologic examination of these animals did not identify any lesions attributable to hypervitaminosis A. Squamous metaplasia of the urinary bladder mucosal epithelium, presumed to be a residual lesion of hypovitaminosis A, was present in varying degrees only in the control group (lower nutritional levels) and those given weekly topical vitamin A (group 3). These findings indicate that vitamin A administration at the above dosages does not result in histopathologic lesions associated with vitamin A toxicity. Increased oral supplementation and every-other-day topical administration may be the most effective methods of reversing hypovitaminosis A-induced lesions.

Acknowledgments

The authors would like to thank Ms. Katie Kingham and the histology lab at the University of Florida.

Literature Cited

1.  Sim, R.R., K.E. Sullivan, E.V. Valdes, G.J. Fleming, and S.P. Terrell. 2009. Comparison of oral and topical vitamin A supplementation in African foam-nesting frogs (Chiromantis xerampelina). Abstr. In: Proc. Am. Assoc. Zoo Vet./Am. Assoc. Wildl. Vet./Am. Zoo Aquar. Assoc. Nutr. Advisory Group Joint Conf. 2009. Tulsa, Oklahoma.