Temporal surge of glycosyltransferase activities in the genital tract of the hamster during the estrous cycle.

ABSTRACT

Mammalian spermatozoa must undergo maturational changes between the events of mating and fertilization. These biochemical and functional alterations, collectively termed capacitation, take place as spermatozoa traverse the female reproductive tract. The preparatory biochemical changes include removal, modification, and reorganization of sperm surface molecules. Although details of all the changes are not known, lectin binding studies have provided evidence suggesting that carbohydrate moieties of sperm surface glycoproteins are modified during capacitation. In an attempt to gain insight into the potential modifications of sperm plasma membrane glycoproteins, we quantified glycoprotein-modifying enzyme activities in the uterine and oviductal fluid of the hamster during the 4 days of the estrous cycle. These enzymes are known to modify existing glycoproteins, either by adding sugar residues (glycosyltransferases) or by removing terminal sugar residues (glycosidases). Data from these studies showed that 1) levels of all glycosyltransferase activities assayed (sialyltransferase, fucosyltransferase, galactosyltransferase, and N-acetylglucosaminyltransferase) were negligible in the uterine fluid at the onset of ovulation (Day 1) but sharply increased preceding ovulation (Day 4); 2) levels of the four glycosyltransferase activities assayed were higher in the oviductal fluid at the onset of ovulation (Day 1) and then gradually decreased through the remainder of the estrous cycle (Day 2 to Day 4); 3) levels of all glycohydrolase activities (acidic alpha-D-mannosidase, beta-D-galactosidase, beta-D-glucuronidase, beta-D-glucosaminidase, and alpha-L-fucosidase) and protein in the uterine and oviductal fluids did not vary widely during the 4 days of the cycle. These results demonstrate a temporal surge of glycosyltransferase activities in the genital tract fluids of the hamster. The temporal changes in the glycoprotein-modifying enzymes may have an effect on the glycosylation of sperm plasma membrane and zona pellucida glycoproteins at the site of fertilization or may alter the surface glycoproteins of the fertilized egg in the uterus prior to implantation.