Retinoic acid can be produced by oxidation in the body from either retinal or retinol, but, once produced, cannot be reduced again.
Retinoic acid is responsible for all of the activity of vitamin A, save visual pigment effects, which require retinal (retinaldehyde), and for effects that require retinol in both the male and female reproductive tracts. Thus, if animals are fed only retinoic acid but no vitamin A (retinol or retinal), they suffer none of the growth-stunting or epithelial-damaging effects of lack of vitamin A (including no xerophthalmia-- dryness of the cornea), but they do suffer retina degeneration and blindness, due to pure retinal (retinaldehyde) deficiency.
Vitamin A-deprived retinoic acid-supplemented male rats exhibit hypogonadism and infertility; similar treatment of female rats causes infertility due to fetal resorption.
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"Retinoic acid"
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