PROBLEM: The distribution and physiological role of calpains in human sperm
METHOD OF STUDY: Semen collected manually from healthy donors was liquefied
then centrifuged by percoll gradient centrifugation. After exposure to dif
ferent concentrations of Ca2+ ionophore A(23187), the samples were used for
immunostaining sodium dodecyl sulfate polyacrylamide gel electrophoresis,
and western blot analysis. It was speculated from the results of the study
using calpain-specific inhibitors that calpain contributes to the sperm mot
ility and acrosome reaction.
RESULTS: With the anti-pro mu -calpain antibody, sperm were immunostained,
whereas all were negative for anti-pro m-calpain antibody binding. Stained
sperm were classified into four types according to the staining pattern: ac
rosome type, equatorial segment type, whole head type, and neck and tail se
gments type. Western blot analysis of sperm homogenate revealed a single 80
-kDa band using the anti-pro mu -calpain antibody, its dose-dependent reduc
tion with Ca2+ ionophore A(23187) suggesting activation by this treatment.
In the presence of membrane permeable calpain inhibitors, sperm motility an
d acrosome reaction were significantly suppressed.
CONCLUSION: These results indicate that mu -calpain may play pivotal roles
in the process of fertilization of human sperm.