title: Relationship between bicarbonate and cyclic nucleotide in the promoting effects on head-to-head agglutination in boar spermatozoa.
abstract: OBJECTIVE
  To clarify the relationship between bicarbonate and cAMP in the promoting effects on the sperm agglutination.
  
  
  METHODS
  Spermatozoa were collected from mature boars, washed and resuspended in a modified Krebs-Ringer HEPES lacking calcium chloride (mKRH). The sperm suspensions were incubated in a water bath (38.5 degrees C) for 60 min and then the percentage of head-to-head agglutinated spermatozoa was determined.
  
  
  RESULTS
  Supplementation of the mKRH with sodium bicarbonate (5-10 mM) significantly raised the percentage of head-to-head agglutinated spermatozoa in the samples. The addition of selective inhibitors for calcium/calmodulin-dependent phosphodiesterases (type 1: 8-methoxymethyl-IBMX and vinpocetine, 25-50 micro M) or for cAMP-specific phosphodiesterases (type 4: Ro20-1724 and rolipram, 25-50 microM) enhanced the effect of bicarbonate on sperm agglutination as highly as did the addition of non-selective inhibitors for phosphodiesterases (IBMX and papaverine, 25-50 microM). A calmodulin antagonist (W-7, 2 microM), that potentially blocks the stimulator of the calcium/calmodulin-dependent phosphodiesterases, significantly enhanced the effect of bicarbonate on sperm agglutination. Moreover, a phosphodiesterase-resistant cAMP analogue (cBiMPS, 0.1 mM) markedly induced agglutination in more spermatozoa (76%) after the incubation without bicarbonate and phosphodiesterase inhibitors than did a less potent cAMP analogue (dibutyryl cAMP, 1 mM) (21%), while three kinds of cGMP analogues (0.1-1 mM) had no effect on sperm agglutination. In addition, a cAMP antagonist (Rp-cAMPS, 1 mM) significantly reduced the sperm agglutination resulting from the actions of bicarbonate and IBMX. On the other hand, the effect of bicarbonate was abolished by a change of incubation temperature from 38.5 degrees C to 25 degrees C.
  
  
  CONCLUSIONS
  These findings demonstrate that the bicarbonate-induced agglutination of boar spermatozoa is controlled via the cAMP-mediated, temperature-dependent signaling cascade. This cascade is suppressed by the action of the phosphodiesterase (at least types 1 and 4).
authors.affiliation: Department of Life Science, Graduate School of Science and Technology, Kobe University, Kobe 657-8501, JAPAN. harayama@ans.kobe-u.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Harayama
authors.forename: Seishiro
authors.initials: S
authors.lastname: Kato
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology*; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology*; D008297:Male; D010208:Papaverine / Q000494:pharmacology; D058915:Purinergic P1 Receptor Antagonists; D017693:Sodium Bicarbonate / Q000494:pharmacology*; D013073:Sperm Agglutination / Q000187:drug effects / Q000502:physiology*; D013077:Sperm Head / Q000187:drug effects / Q000502:physiology*; D013552:Swine; D013806:Theophylline / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D058915:Purinergic P1 Receptor Antagonists; C016276:8-bromocyclic GMP; C053907:8-cyclopentyl-1,3-dimethylxanthine; D003994:Bucladesine; D017693:Sodium Bicarbonate; D013806:Theophylline; D010208:Papaverine; D000242:Cyclic AMP; D006152:Cyclic GMP; D015056:1-Methyl-3-isobutylxanthine