The activating effects of bicarbonate on sperm motility and respiration at ejaculation.
ABSTRACT Mature porcine sperm preserved in the cauda epididymis are quiescent. At ejaculation, they are mixed with the seminal vesicle fluid containing HCO3- and are rapidly activated. The role of HCO3- on the sperm activation process at ejaculation was studied in vitro. HCO3- quickly increased the motility, respiration rate and cAMP content of the porcine epididymal sperm. The extent of activation was proportional to the pCO2 in the medium. The activating effect of HCO3- on the motility was observed even in the absence of fructose as well as in the presence of KCN. 8-Bromoadenosine 3',5'-cyclic monophosphate and theophylline showed similar activating effects to that of HCO3-. However, HCO3(-)-free seminal plasma, Ca2+, amino acids, intermediates of the Krebs cycle, substrates of respiration and increases in the intracellular pH, extracellular pH or ionic strength of the medium had no effect. Fructose sustained the active state of the sperm and gradually increased both the motility and respiration rate when the dose of HCO3- was low. The anion channel blocker enhanced the activating effect of HCO3-. These results suggest that, upon ejaculation, HCO3- is a unique activator in vivo which makes the quiescent sperm motile via the HCO3(-)-adenylate cyclase-cAMP system, to which an endogenous HCO3- derived from metabolic CO2 may be related.
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ABSTRACT: The solute carrier 26 (SLC26) family emerges as a distinct class of anion transporters with its members SLC26A3 (Slc26a3) and SLC26A6 (Slc26a6) reported to be electrogenic Cl(-) /HCO3 (-) exchangers. While it is known that uterine fluid has high HCO3 (-) content and that HCO3 (-) is essential for sperm capacitation, the molecular mechanisms underlying the transport of HCO3 (-) across uterine epithelial cells and sperm have not been fully investigated. The present review re-examines the results from early reports studying anion transport, finding clues for the involvement of Cl(-) /HCO3 (-) anion exchanges in electrogenic HCO3 (-) transport across endometrial epithelium. We also summarize recent work on Slc26a3 and Slc26a6 in uterine epithelial cells and sperm, revealing their functional role in working closely with the cystic fibrosis transmembrane conductance regulator (CFTR) for HCO3 (-) transport in these cells. The possible involvement of these anion exchangers in other HCO3 (-) dependent reproductive processes and their implications for infertility are also discussed.Cell Biology International 09/2013; · 1.64 Impact Factor
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ABSTRACT: Storage of liquid-preserved boar spermatozoa is associated with a loss of fertilising ability of the preserved spermatozoa, which standard semen parameters barely reflect. Monitoring responses to molecular effectors of sperm function (e.g. bicarbonate) has proven to be a more sensitive approach to investigating storage effects. Bicarbonate not only initiates capacitation in spermatozoa, but also induces motility activation. This occurs at ejaculation, but also happens throughout passage through the oviduct. In the present study we tested whether the specific response of boar sperm subpopulations to bicarbonate, as assessed by motility activation, is altered with the duration of storage in vitro. Three ejaculates from each of seven boars were diluted in Beltsville thawing solution and stored at 17°C. Only minor changes in the parameters of diluted semen were revealed over a period of 72h storage. For assessment of bicarbonate responses, subsamples of diluted spermatozoa were centrifuged through a discontinuous Percoll gradient after 12, 24 and 72h storage. Subsequently, spermatozoa were incubated in two Ca2+-free variants of Tyrode's medium either without (TyrControl) or with (TyrBic) 15mM bicarbonate, and computer-aided sperm analysis motility measurements were made. Cluster analysis of imaging data from motile spermatozoa revealed the presence of five major sperm subpopulations with distinct motility characteristics, differing between TyrBic and TyrControl at any given time (P<0.001). Although there was an increasing loss of motility function in both media, bicarbonate induced an increase in a 'fast linear' cohort of spermatozoa in TyrBic regardless of storage (66.4% at 12h and 63.9% at 72h). These results imply a binary pattern in response of sperm motility function descriptors to storage: although the quantitative descriptor (percentage of motile spermatozoa) declines in washed semen samples, the qualitative descriptor (percentage of spermatozoa stimulated into fast linear motion by bicarbonate) is sustained independent of the duration of storage.Reproduction Fertility and Development 06/2014; 26(5):623-32. · 2.58 Impact Factor
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ABSTRACT: Sperm intracellular pH, membrane voltage and calcium concentration [Ca2+]i are all important for sperm activity within the female reproductive tract.•Ion homeostasis and membrane voltage are under control of sperm ion channels and transporters. They regulate sperm motility and ability to locate and fertilize an egg.•Sperm ion channels are diverse and could differ between species in respect to their regulation.•Here we discuss the current knowledge about flagellar ion channels of mammalian sperm and concentrate our attention on calcium channel CatSper, proton channel Hv1, potassium channels of Slo family, and several new emerging ion channels.Cell Calcium 10/2014; · 4.21 Impact Factor