Capacitation of spermatozoa, a complex process occurring after sperm ejaculation, is required to produce fertilization of the oocyte in vivo and in vitro. Although this process results from a poorly understood series of morphological and molecular events, protein tyrosine phosphorylation has been associated with sperm capacitation in several mammalian species, but it still remains to be demonstrated in ram spermatozoa. Studies of capacitation in ram spermatozoa are of great interest, since several reports have suggested that the reduced fertility of cryopreserved spermatozoa is due to their premature capacitation. In this work, we report for the first time, to our knowledge, that tyrosine phosphorylation of ram sperm membrane proteins is related to the capacitation state of these cells. Capacitation induced tyrosine phosphorylation of some plasma membrane proteins of ram spermatozoa freed from seminal plasma by a dextran/swim-up procedure. It has also been proved that cold-shock induces protein tyrosine phosphorylation as well as a decrease in plasma membrane integrity. Addition of seminal plasma proteins prior to cold-shock not only improved sperm survival but also promoted a decrease in protein tyrosine phosphorylation.
Copyright 2002 Wiley-Liss, Inc.