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Effects of dietary vitamin A intake on acrosin- and plasminogen-activator activity of ram spermatozoa

Laboratory of Physiology, School of Veterinary Medicine, University of Thessaly, Karditsa, Greece, ¹ Laboratory of Physiology, School of Veterinary Medicine, Aristotle University of Thessaloniki, University Campus, 541 24 Thessaloniki, Greece, ² Laboratory of Physiology, Department of Animal Production, Technological Educational Institute of Epirus, Arta, Greece and ³ Department of Animal Production, Technological Educational Institute, Larissa, Greece

Correspondence should be addressed to I A Taitzoglou; Email: jotai{at}vet.auth.gr

Acrosin and plasminogen activators are proteolytic enzymes of ram spermatozoa that play an essential role in the induction of the acrosome reaction, as well as the binding of spermatozoa to the oocyte and their penetration through the layers that surround the oocyte. Since vitamin A can alter gene expression in various tissues, testis included, this study was undertaken to evaluate the possible effect of vitamin A intake on acrosin- and plasminogen-activator activity. During a 20-week experiment, 15 rams of the Greek breed Karagouniki, divided to three groups, received different amounts of vitamin A per os in retinyl acetate capsules (group A, controls, 12 500 iu/animal per day; group B, 50 000 iu/animal per day; group C, 0 iu/animal per day up to the 13th week, then 150 000 iu/animal per day until the end of the experiment). Acrosin- and plasminogen-activator activity were determined by spectrophotometric methods. Vitamin A was determined in blood plasma by HPLC. No statistical differences were detected regarding the body weight of the rams or the qualitative and quantitative parameters of their ejaculate throughout the whole experiment. No statistically significant alterations of enzyme activity were detected in group B. In group C, both enzyme activities started declining in week 9. Compared with controls, maximum reduction for acrosin was 49% on week 11 and for plasminogen activators 51% in week 14. Activities returned to normal rates after vitamin A resupplementation. To date, the main result of vitamin A deficiency was known to be arrest of spermatogenesis and testicular degeneration. A new role for vitamin A may be suggested, since it can influence factors related to male reproductive ability before spermatogenesis is affected.