The role of glucose in supporting motility and capacitation in human spermatozoa

Glucose has been reported to be beneficial to human sperm for optimal capac itation and fertilization, although it is unclear whether glucose is requir ed for providing extra metabolic energy through glycolysis, or for generati ng some other metabolic product. In this study, the effects of sugars on hu man sperm capacitation, motility, and energy production were investigated. The glucose concentration that supported the greatest number of acrosome re actions was 5.56 mmol L-1. Compared with incubations with no added sugar, t his concentration of glucose, fructose, mannose, or galactose appeared to s lightly increase the number of acrosome reactions occurring after 18 hours of capacitation, or following induction by 2 mu mol A23187 + 3.6 mmol pento xifylline L (1), but only glucose had a statistically significant effect. G lucose supported increased penetration of zona-free hamster oocytes, but it s advantage was not statistically significant. The addition of 5.56 mmol gl ucose or fructose L (1) to sugar-free medium immediately increased the aden osine triphosphate (ATP) concentration and motility of sperm. These paramet ers were then stable for 3 hours, but declined markedly after 18 hours. In the absence of a glycolysable sugar, motility began to decline in the first hour and only 2% or 3% of sperm remained motile after 18 hours. Glucose or fructose was required to support hyperactivated motility. 2-Deoxyglucose w as detrimental to the ATP concentration and motility of sperm, and supporte d fewer spontaneous or progesterone-stimulated acrosome reactions than were observed in the absence of a sugar. We conclude that glycolytic ATP produc tion is required for vigorous motility and hyperactivation in human sperm. Other products of glucose metabolism are not essential to support capacitat ion, but they may have a small, enhancing effect.