Motility activation and second messenger signalling in spermatozoa from rat cauda epididymidis

Abstract

This study examined molecular mechanisms involved in the activation of motility in spermatozoa from the cauda epididymidis of rats. A 1.05-fold dilution of semen from the cauda epididymidis with 300 mmol sucrose l −1 did not activate motility in spermatozoa. Addition of dibutyryl cAMP, pentoxifylline or Ca 2+ to the sucrose activated motility in the short term (< 30-60 min). A fivefold dilution of semen from the cauda epididymidis with a modified Tyrode's medium (BWW) activated and sustained vigorous motility that could not be attenuated with kinase inhibitors. This motility was associated with a transient increase in intracellular cAMP during the first 60 s of activation. Lower motility was activated in Ca 2+ -deficient media but this was not associated with an increase in cAMP. A fivefold dilution with plasma from the cauda epididymidis did not activate motility. The addition of Ca 2+ to the sucrose induced an increase in cAMP of similar duration but lower magnitude to that associated with dilution in BWW. The results from this study indicate that the cAMP and Ca 2+ signal transduction pathways are involved in activation of sperm motility, and that the increase in intracellular cAMP in rat spermatozoa from the cauda epididymidis undergoing motility activation is Ca 2+ -dependent. This is the first study to report a Ca 2+ -dependent increase in cAMP associated with motility activation in immotile mammalian spermatozoa. In light of these data, a model is proposed whereby cAMP and Ca 2+ act as synarchic messengers, initiating a signal transduction cascade, which is independent of protein kinase A-mediated phosphorylation of flagella proteins in immotile spermatozoa from the cauda epididymidis.

The role of Zn-α2 glycoprotein in sperm motility is mediated by changes in cyclic AMP

“…Such motility is regulated by the surrounding environment; obvious changes in motility include activation, hyperactivation, and chemoattraction in various species (Ahmad et al 1995, Ho & Suarez 2001, Wang et al 2001, Wade et al 2003. The cyclic AMP (cAMP)/cAMP-dependent protein kinase A (PKA) signaling pathway and the calcium signaling pathway are generally recognized as the two signaling pathways most central to the regulation of mammalian sperm motility (Brokaw 1987, Wishart & Ashizawa 1987, San Agustin & Witman 1994, Wade et al 2003. Even though the role of these signaling pathways in sperm motility has been demonstrated in many experiments, the specific underlying molecular mechanisms have never been fully explored.…”

Phosphopeptide Analysis of Rodent Epididymal Spermatozoa

“…Backflushing of the epididymis is traditionally performed using water saturated mineral oil and a balanced salt solution in the syringe itself as a medium to remove the spermatozoa [22][23][24][25] If this occurs, it is impossible to continue and the sample is essentially lost. This can be overcome by the use of BWW or other balanced salt solutions in the syringe, however, although this is successful, we soon recognized that many of the spermatozoa become motile as soon as the BWW solution came into contact and mixed with the caudal epididymal cells.…”

The effect of oestradiol-17β on the motility, viability and the acrosomal status of bull sperm

“…One possibility might be the involvement of cAMP signal transduction pathways. It has been reported that these pathways are involved in activation of sperm motility (Armstrong et al, 1994;Wade et al, 2003). This increase in motility is an important factor affecting fertilization, because high rates of ovum fertilization require efficient transport of sperm from the cervix to the oviducts (Hawk et al, 1978).…”