Alterations in sperm protein phosphorylation in male infertility

Protein phosphorylation is involved in sperm capacitation, so the effect of protein phosphatase inhibitors on the capacitation of spermatozoa of males with unexplained infertility was investigated. D-mannose ligand specific r eceptor expression in fresh, living spermatozoa, capacitated or treated wit h calyculin A (an inhibitor of protein phosphatases 1 and 2A), was studied in three groups of men: pre-vasectomy (fertile) males, males in couples wit h male infertility, and males in couples with infertility of unknown actiol ogy. Flow cytometry showed significant differences between infertile couple s with a male factor and fertile couples (P <0.05), both after capacitation and after treatment with calyculin A. In the group of couples with inferti lity of unknown actiology (n = 15), D-mannose receptor expression was dimin ished in six cases after classical capacitation. However, when the spermato zoa of these six men were treated with calyculin A, five showed an increase d specific D-mannose receptor expression. From these results it is suggeste d that in vitro treatment of spermatozoa with inhibitors of protein phospha tases may be of great value in some cases of unexplained infertility.