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Influence of Zinc Deficiency on Retinal Reductase and Oxidase Activities in Rat Liver and Testes^1,2,

Lipids Laboratory, Research Institute, St. Joseph Hospital, Lancaster, Pa. 17604, and Trace Element Research Laboratory, Veterans Administration Hospital, Washington, D.C. 20422

The influence of zinc deficiency on vitamin A metabolism in rats was investigated by assessing two specific enzymes involved in its metabolism viz retinal reductase and retinal oxidase in the liver as well as in the testes. The activity of retinal reductase in the liver was not altered in zinc deficiency. Retinal oxidase activity on the other hand, was increased approximately 1.5 fold over the pair-fed controls. In contrast, both retinal reductase and oxidase in the testes were decreased during zinc deficiency. The effects of zinc deficiency on vitamin A metabolism in the liver could be partly attributed to the secondary effect of reduced food intake and growth. However, the effects seen in the testes on the metabolic enzymes of vitamin A appear to be due to zinc deficiency per se. The liver concentration of vitamin A (µg/g) as well as total vitamin A (µg/liver) were higher in the zinc-deficient rats when compared to the zinc-sufficient rats although not significantly different from the pair-fed controls. In agreement with previous reports, the plasma vitamin A in zinc-deficient rats were found to be markedly lowered compared to zinc sufficient ad libitum controls.

KEY WORDS: • vitamin A • zinc deficiency • retinal reductase • retinal oxidase • liver • testis

¹ Supported in part by U.S. Public Health Service Grant AM 13557 from the National Institute of Arthritis, Metabolism and Digestive Diseases and by Veterans Administration research funds, Washington, D.C., VA Hospital, Project No. 7992-06.

² Submitted in partial fulfillment for the degree of Master of Science in Biology by F. O. Cope to the Graduate School of Millersville State College, Pennsylvania. A preliminary report of this investigation was presented at the 51st Annual Meeting of the Pennsylvania Academy of Sciences, Grove City, Pennsylvania in 1975. Cope, F. O. & Sundaresan, P. R. (1975) The influence of zinc deficiency on vitamin A metabolism in rats. Proc. Penn. Acad. Sci. 49, 95 (Abstr.).

³ Present address: Vitamin and Mineral Nutrition Laboratory, Nutrition Institute, USDA, Beltsville, Maryland 20705. Reprint requests to Dr. J. C. Smith, Jr.

Manuscript received 22 April 1977.