Matrine compromises mouse sperm functions by a [Ca2+]i-related mechanism

• Matrine has no toxicity on testis development and spermatogenesis of male mice.
• Matrine inhibits motility, capacitation and progesterone-induced AR of mouse sperm.
• Matrine reduces mouse sperm intracellular Ca2+ concentration.
• Matrine decreases mouse sperm CatSper current.
• Matrine down-regulates the expression of CatSper genes in mouse testes.

Matrine, a bioactive alkaloid widely used in Chinese medicine, inhibits mouse sperm functions in vitro. In this study, we investigated the reproductive toxicity of matrine to male mice in vivo. C57BL/6J mice were administered with daily doses of 0, 1, 10 and 50 mg/kg matrine by intraperitoneal injection for 30 days. The results showed that matrine did not affect testis size, testis weight, sperm count and sperm viability, but it significantly inhibited total motility, progressive motility, linear velocity, capacitation and the progesterone-induced acrosome reaction of mouse sperm. Furthermore, the intracellular Ca2+ concentration ([Ca2+]i), a key regulator of sperm function, was reduced in sperm of matrine-exposed mice. The current and gene expression of the sperm specific Ca2+ channel, CatSper, which modulates Ca2+ influx in sperm, were decreased in testes of matrine-exposed mice. These results indicate that matrine inhibits mouse sperm functions by a [Ca2+]i-related mechanism via CatSper channel.