Role of potassium and pH on the initiation of sperm motility in the European eel

Abstract

The role of potassium from the seminal plasma and/or the activation media was examined by selectively removing K from this media, and by testing the use of K channel inhibitors and a K-ionophore. Sperm motility was measured using a CASA system, intracellular K and pH were measured by flow cytometry, and sperm head area was measured by ASMA: Automated Sperm Morphometry Analyses. Sperm motility was notably inhibited by the removal of K from the seminal plasma and by treatment with the K ionophore valinomycin. This therefore indicates that a reduction of K levels in the quiescent stage inhibits further motility. The normal decrease in sperm head area induced by seawater activation was altered by the removal of K from the seminal plasma, and an increase in the pH in the quiescent stage was also induced. Intracellular pH (pH) was quantitatively measured for the first time in European eel spermatozoa, being 7.2 in the quiescent stage and 7.1 post-activation. Intracellular and external pH levels influenced sperm motility both in the quiescent stage and at activation. The alkalinization of the pH (by NHCl) inhibited sperm motility activation, while acidification (by Na-acetate) did not have any effect. Our results indicate that a pH gradient between the sperm cell and the seminal plasma is necessary for sperm motility activation. The presence of the ion K in the seminal plasma (or in the extender medium) is necessary in order to maintain sperm volume, intracellular pH and sperm motility.

Intracellular pH regulation and sperm motility in the European eel

“…That is, motility activation with ASW at pH 8.2 induced an intracellular alkalinization, when the sample was diluted at pHe<8.0, an acidification when pHe>8.0 or no pHi variation, when pHe was 8.0. Probes Instructions, and also different from the pKa calculated by our group [8] for SNARF-5F AM in European eel sperm, which was 7.16. In that case, the pH calibration was performed in only one sperm sample, while in the present experiment the calibration was repeated 5 times, using 5 different samples.…”

“…However, other authors [6] suggested the opposite for another marine fish, the Japanese eel (Anguilla japonica), with an H + uptake (then an internal acidification) triggering sperm motility. Our group observed a decrease in sperm pHi post-activation in a closed species, the European eel (Anguilla anguilla; [7]) which was later confirmed [8]. In terms of freshwater fish species, hypoosmotic shock was accompanied by a fast alkalinization of the sperm cells in common carp [9].…”

“…If that is confirmed, it will be different to carp, where the sperm is almost depolarized in the quiescent stage (-2.6 mV; [16] and hyperpolarized (to -29 mV) after freshwater activation. It is predicted that eel motility initiation could also involve changes in membrane voltage, as an increase in [K + ]i has been observed at activation [8]. This voltage change should be studied further.…”

Comparison of European eel sperm cryopreservation protocols with standardization as a target

“…Although the samples were frozen immediately after the addition of the freezing media containing DMSO to the sperm, it has been proved that the presence of DMSO in the freezing media activates the European eel sperm (Peñaranda et al, 2009), and lead to a reduced post-thawed sperm motility. Even though the DMSO protocol was improved to reduce activation by increasing the concentration of NaHCO3, decreasing the pH of the media (Peñaranda et al, 2009;Vílchez et al, 2017), fast manipulation was still required. In this study, we show that the sperm was activated after diluting in the freezing media (before freezing) containing DMSO.…”

The Catsper channel and its roles in male fertility: a systematic review

“…Among them, the SLO3 channel is a sperm-specific and pH-sensitive K + channel. Similar to the Catsper channel, SLO 3 is also strongly related to sperm hyperactivity and motility [ 34 , 35 ]. Another crucial function of the SLO 3 channel that affects the Catsper channel is to maintain the current balance of flagella in the spermospore [ 8 ].…”