Transient Ca2+ mobilization caused by osmotic shock initiates salmonid fish sperm motility

Abstract

Hayashi et al., 1987;Inaba et al., 1998). However, Morita and colleagues (Morita el al., 2005) reported that treatment of sperm with a 10% glycerol solution, before subsequent dilution into a low-osmotic solution, induced the , using fluo-4, revealed that intracellular Ca 2+ increased when sperm were suspended in hypertonic solutions, and a subsequent dilution into a hypotonic solution led to a decrease in intracellular Ca 2+ concomitant with motility initiation. In addition, upon dilution of sperm into a hypertonic glycerol solution prior to demembranation, the motility of demembranated sperm was reactivated in the absence of cAMP. The motility recovery suggests that completion of axonemal maturation occurred during exposure to a hypertonic environment. As a result, it is likely that glycerol treatment of sperm undergoing hypertonic shock causes mobilization of intracellular Ca 2+ from the intracellular Ca 2+ store and also causes maturation of axonemal proteins for motility initiation. The subsequent dilution into a hypotonic solution induces a decrease in intracellular Ca 2+ and flagellar movement. This novel mechanism of sperm motility initiation seems to act in a salvaging manner for the well-known K + -dependent pathway.

Coordinated Action of Aquaporins Regulates Sperm Motility in a Marine Teleost1

“…In teleost spermatozoa, the increase of [Ca 2+ ] i can be caused by external influx via Ca 2+ channels, Ca 2+ pumps or Na + /Ca 2+ exchangers [33,[39][40][41][42], as a consequence of the activation of stretchactivated channels that can transport Ca 2+ together with K + or activate Ca 2+ channels [6,7,43,44], or by the release of Ca 2+ from intracellular stores [43,[45][46][47]. A previous study reported that the spermatozoa of gilthead seabream and striped seabream (Lithognathus mormyrus) can be activated in non-ionic solutions and that several K + and Ca 2+ channel blockers have no effect on the initiation of sperm motility in SW, suggesting that neither external K + nor Ca 2+ play a significant role [25].…”

Thermosensitive ion channel TRPV1 is endogenously expressed in the sperm of a fresh water teleost fish (Labeo rohita) and regulates sperm motility

“…17 Notably, the Ca 2+ -signaling experienced by the sperm cells is variable and this variability often correlates with species differences, morphology of the sperm cells and the environment where the sperms are released. 4,18 Recently, a number of studies have demonstrated that Transient Receptor Potential (TRP) family of channels present in neurons can conduct Ca 2+ influx in response to different physical factors such as temperature, osmotic pressure, pH and light. 19 In addition, these channels can detect a battery of signaling molecules and thus contribute to the chemosensory processes relevant for neuronal guidance and contact formation.…”

Tubulin-dynein system in flagellar and ciliary movement

“…139,140) Since the motility initiation is tightly associated with the transient increase of intracellular Ca 2+ concentration, it is plausible that a Ca 2+ -dependent mechanism might be common to the motility activation in teleost sperm.…”