ryanodine and butabindide

Recent studies have identified Ca(2+) stores in sperm cells; however, it is not clear whether these Ca(2+) stores are functional and how they are mobilized. Here, in vitro and in vivo, we determined that tripeptidyl peptidase II antagonists strongly activated the cAMP/PKA signaling pathway that drives sperm capacitation-associated protein tyrosine phosphorylation. We demonstrated that in the absence of Ca(2+), TPIII antagonists elevated the intracellular Ca(2+) levels in sperm, resulting in a marked improvement in sperm movement, capacitation, acrosome reaction, and the in vitro fertilizing ability. This antagonist-induced release of intracellular Ca(2+) could be blocked by the inhibitors of ryanodine receptors (RyRs) which are the main intracellular Ca(2+) channels responsible for releasing stored Ca(2+). Consistent with these results, indirect immunofluorescence assay using anti-RyR antibodies further validated the presence of RyR3 in the acrosomal region of mature sperm. Thus, TPPII can regulate sperm maturation by modulating intracellular Ca(2+) stores via the type 3 RyR.

Topics: Acrosome Reaction; Amino Acid Chloromethyl Ketones; Aminopeptidases; Animals; Blotting, Western; Calcium; Cells, Cultured; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Dantrolene; Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; Indoles; Intracellular Space; Male; Mice; Mice, Inbred C57BL; Muscle Relaxants, Central; Phosphorylation; Ryanodine; Ryanodine Receptor Calcium Release Channel; Serine Endopeptidases; Signal Transduction; Sperm Capacitation; Spermatozoa