Analysis of calmodulin acceptor proteins and the influence of calmodulin antagonists on human spermatozoa

R. J. Aitken, J. S. Clarkson, M. J. Hulme, C. J. Henderson

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    The possible role of calmodulin in regulating a number of calcium-dependent functions exhibited by human spermatozoa was investigated by using the antagonists trifluoperazine and calmidazolium. At high doses both antagonists inhibited the motility of human spermatozoa and induced a concomitant rise in [Ca2+]i and a decline in cAMP. Lower doses of these antagonists, particularly calmidazolium, suppressed the ability of human spermatozoa to generate reactive oxygen species and exhibit sperm-oocyte fusion, without influencing [Ca2+]i, cAMP, or motility. This inhibition of sperm-oocyte fusion was effective even if the spermatozoa were subsequently exposed to A23187, suggesting that calmodulin may regulate this aspect of human sperm function at a point downstream from calcium influx.

    Both radiolabelling and affinity chromatography techniques were used to detect a number of calcium-dependent and calcium-independent calmodulin acceptor proteins in the human spermatozoon. The major calcium-dependent acceptor proteins exhibited Mr values of 32,000 and 22,000–27,000, respectively, and did not appear to be associated with the sperm plasma membrane.
    Original languageEnglish
    Pages (from-to)93-111
    Number of pages19
    JournalGamete Research
    Issue number1
    Publication statusPublished - Sept 1988


    • sperm-oocyte fusion
    • Reactive oxygen species
    • Motility
    • Calcium
    • cAMP


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