Abstract
Sperm motility patterns are continuously changed after ejaculation to fertilization in the female tract. Hyperactivated motility is induced with high glucose medium in vitro or the oviduct fluids in vivo, whereas sperm maintain linear motility in the seminal plasma or the uterine fluids containing low glucose. Therefore, it is estimated that sperm motility patterns are dependent on the energy sources, and the mitochondrial oxidative phosphorylation is activated to produce ATP in low glucose condition. To elucidate these hypotheses, boar sperm was incubated in different energy conditions with the transcription and translation inhibitors in vitro. Sperm motility parameters, mitochondrial activity, ATP level, gene expression and protein synthesis were analyzed. Sperm progressive motility and straight-line velocity were significantly increased with decreasing glucose level in the incubation medium. Moreover, the mitochondrial protein turnover meaning transcription and translation from mitochondrial genome in sperm is activated during incubation. Incubation of sperm with mitochondrial translation inhibitor (D-chloramphenicol) suppressed mitochondrial protein synthesis, mitochondrial activity and ATP level in sperm and consequently reduced the linear motility speed, but not the motility. Thus, it is revealed that the mitochondrial central dogma is active in sperm, and the high-speed linear motility is induced in low glucose condition via activating the mitochondrial activity for ATP generation.
Highlights
Mammalian spermatozoa reside in the female genital tracts for several hours from ejaculation to fertilization process
The sperm motility tracks generated by Computer-Assisted Sperm Analysis (CASA) revealed that the incubation in high glucose media made circle-like tracks, while low glucose condition made it linear-like tracks (Figure 1A)
In this study, using the medium containing different doses of glucose we revealed that mitochondrial activity was increased under low glucose condition, and the ATP produced in mitochondria was associated with a high-speed linear motility in boar sperm
Summary
Mammalian spermatozoa reside in the female genital tracts for several hours from ejaculation to fertilization process. As defined by low lateral amplitude and high straight-line velocity, is essential for sperm migration from the cervix to the uterus and to oviduct (Shalgi et al, 1992; Suarez and Pacey, 2006). The capacitated sperm show hyperactivated status (Suarez, 2008), defined as high curvilinear velocity as well as high lateral amplitude, and penetrate the oocyte for successful fertilization (Stauss et al, 1995). Sperm motility patterns are dependent on flagellar motion; the symmetry flagellar motion induces the linear motility pattern, whereas the asymmetry one is associated with hyperactivation (Phillips, 1972; Suarez et al, 1991; Ho et al, 2002; Curtis et al, 2012). The sliding filament theory is adapted to sperm flagella, namely the sperm motility is induced by ATP production (Huxley and Niedergerke, 1954; Summers and Gibbons, 1971; Brokaw, 1972)
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