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Interaction of zinc and vitamin A on the ocular surface
Suketaka Kanazawa1, Takashi Kitaoka, Yoshiko Ueda
1Department of Ophthalmology and Visual Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan. Suketaka.Kanazawa@mb6.seikyou.ne.jp
Purpose:
The purpose of this study was to assess morphologically the interaction between zinc and vitamin A in their effect on the ocular surface.
Methods:
Three-week-old Wistar Kyoto rats were divided into five groups: group A(+) Zn(+) was fed a diet containing both vitamin A and Zn; group A(-) was fed a vitamin A-deficient diet; group A(-) Zn(+) was given a vitamin A-deficient diet and deionized distilled water with Zn; group Zn(-) and group Zn(-) A(+) were fed a Zn-deficient diet, whereby group Zn(-) A(+) received an intraperitoneal injection of vitamin A. Corneas and conjunctivas of each group were examined by electron microscopy.
Results:
The corneas and conjunctivas of group A(-) demonstrated a decrease in the number of microvilli in the epithelium. The corneas and conjunctivas of group A(-) Zn(+) had a decrease in microvilli but more microvilli than those of group A(-). The corneas of group A(-) showed keratinization, but those of group A(-) Zn(+) showed no keratinization. In group Zn(-) the microvilli on the conjunctiva and cornea were sparse. Group Zn(-) A(+) had a decrease in microvilli but more microvilli than group Zn(-). The conjunctivas of group Zn(-) A(+) had more goblet cells with granules than did those of group Zn(-).
Conclusion:
These results suggest that a synergistic interaction exists between vitamin A and zinc for the maintenance of the corneal and conjunctival epithelium.