Acrosome Reaction Changes the Pattern of Cyclic Nucleotide Phosphodiesterases in Human Sperm

Abstract

Three categories of cyclic nucleotide phosphodiesterases (cNPDE) are distinguished at present: type 1 with high affinity to cyclic GMP; type 2 with low affinity to cyclic AMP and to cyclic GMP; and type 3 with high affinity to cyclic AMP. For the evaluation of normal values in human spermatozoa 50 semen samples with normal classical semen parameters were investigated. The activities (means ± SD) of the cNPDE types (10⁻¹¹ mol/10 min × 10⁸ spermatozoa) of washed human spermatozoa amounted to 47 ± 22 (type 1), 3350 ± 1537 (type 2), and 70 + 38 (type 3). A significant inhibition of type 3 by cyclic GMP could not be detected. One milligram protein of the spermatozoa hydrolyzed about 20-fold the amount of cyclic nucleotides compared with 1 mg protein of the seminal plasma. Furthermore, the cNPDE of the spermatozoa and of the seminal plasma differed in the influence of type 3 by cyclic GMP and in the pattern of activities. The acrosome reaction (AR) induced by the cold shock method led to an activation of type 2 and 3 unlike the initiation of the AR by the digitonin method. The latter did not cause significant differences of the cNPDE activities before and after the AR.

Key Words:

• Human spermatozoa
• Cyclic nucleotide phosphodiesterase pattern
• Acrosome reaction.