Evidence for a functional glycogen metabolism in mature mammalian spermatozoa

The glycogen content in fresh raw dog spermatozoa was 0.22 +/- 0.03 mu mol/ mg protein. This matched with the presence of a glycogen-like staining in t he head and midpiece. Glycogen levels lowered to 0.05 mu mol/mg protein aft er incubation for 60 min without sugars. Addition of either 10 mM fructose or 10 mM glucose increased glycogen content to 0.70 mu mol/mg protein. On t he other hand, glycogen synthase activity ratio of fresh dog sperm (0.35 +/ - 0.07, measured in the absence and the presence of glucose 6-P) increased to 0.55 with 10 mM fructose for 20 min, whereas glucose had a smaller effec t. Spermatozoa extracts had also a protein of about 100 Kd, which reacted a gainst a rat liver glycogen synthase antibody. This was located in sperm he ad and midpiece. Furthermore, glycogen phosphorylase activity ratio measure d in presence and absence of AMP (0.25 +/- 0.03 in fresh samples) decreased to 0.15 by 10 mM glucose for 20 min, whereas fructose was less potent in t his regard. The maximal effect of glucose and fructose were observed from 1 0-20 mM onwards. This work is the first indication for a functional glycoge n metabolism in mammal spermatozoa, which could play an important role in r egulating sperm survival in vivo. Mel. Reprod. Dev. 56:207-219, 2000. (C) 2 000 Wiley-Liss, Inc.