Ascorbic acid and reproduction in fish: endocrine regulation and gamete quality

High ascorbic acid concentrations have been associated with gonad and brain tissues in teleost fishes. Although a direct dietary effect on gamete qual ity has been given some attention recently, the mechanism of action of asco rbate along the cascade of reproductive events in the hypothalamus, pituita ry and gonads has not been defined. Data relating to gamete production and quality, as well as a possible protective role for ascorbate against cumula tive genetic defects during gametogenesis and congenital malformation durin g gestation (embryonic development) is reviewed. It is suggested that the g onad growth in response to gonadotropin stimulation involves direct interac tion between catecholamines and steroid hormones and their receptor sites. This interaction acts as a regulatory mechanism of ascorbate absorption, tr ansfer and metabolism (degradation and/or renewal) in the reproductive syst em. We conclude that ascorbic acid is a leading nutrient in reproductive ti ssue functions and further research is needed on: (1) its antioxidant effec t on gametes' (sperm and ova) capacity to prevent DNA damage occurring prio r to (endogenous) and after spawning (environmental insults); (2) its dieta ry requirement to optimize survival and physiological recovery in multiple spawners; (3) the integration mechanism of ascorbic acid action as part of the overall endocrine regulation of neurohormonal-hormonal pathway in fish reproduction; and (4) the possible role for ascorbate in regulating fish ma turation and/or infertility in the presence of enhanced UV-radiation or con ditions of intensive aquaculture (hypoxia. oxygen supersaturation, dietary pro-, and antioxidants).