Copper: a biphasic regulator of caprine sperm forward progression

Area of Science:

• Reproductive Biology
• Trace Element Metabolism
• Sperm Physiology

Background:

• Copper is vital for spermatogenesis and present in reproductive fluids.
• The specific role of copper in regulating mammalian sperm forward motility remains largely unexplored.
• Sperm forward motility is a critical factor for in vivo fertility.

Purpose of the Study:

• To investigate the physiological role of the bivalent copper ion (Cu2+) on mammalian sperm forward motility.
• To determine the dose-dependent effects of Cu2+ on sperm motility using a caprine model.

Main Methods:

• Utilized a chemically-defined medium and caprine cauda epididymal sperm.
• Assessed sperm forward motility using a spectrophotometric motility assay.
• Measured sperm membrane lipid peroxidation and intra-sperm cyclic adenosine mono phosphate (c-AMP) levels.

Main Results:

• Cu2+ significantly enhanced sperm forward motility in a dose-dependent manner, with maximal activation around 5 µM.
• Higher concentrations (above 10 µM) of Cu2+ led to decreased sperm motility, indicating biphasic regulation.
• Low Cu2+ concentrations increased lipid peroxidation and c-AMP, while high concentrations inhibited both parameters.

Conclusions:

• Cu2+ exerts a biphasic regulatory effect on mammalian sperm forward motility.
• The modulation of sperm motility by Cu2+ is likely mediated by changes in membrane lipid peroxidation, which subsequently affects intra-sperm c-AMP levels.
• These findings elucidate a novel mechanism for copper's role in sperm function and fertility.