We all know that calcium is an essential trace element required by the human body. Calcium deficiency can cause many health problems such as osteoporosis and weakened immunity. In the human body, 99% of calcium is contained in bones and teeth. Will the tiny sperm also lack calcium? Inorganic salt ions ingested by the human body are transported to various tissues and organs through the blood, and the content of various elements in different tissues and organs varies greatly, and the amount of their content depends on the needs of various tissues and organs for different elements. Relevant studies have shown that calcium, magnesium, and potassium in seminal plasma are 4 to 5 times higher than that in serum, and zinc is more than 10 times higher, which can explain the important role of various trace elements in male reproduction.
In order for a sperm to successfully combine with an egg, it not only needs to have the ability to exercise, but also has many difficult processes to go through-“capacitation” and “super activation”. In fact, as early as in the epididymis, the sperm has matured and has the ability to reproduce offspring, but a glycoprotein secreted by the epididymis-an energetic factor attached to the surface of the sperm, inhibits his fertilization ability. When the sperm enters the female reproductive tract, the glycoprotein on the surface of the sperm acrosome is degraded by the enzymes in the female reproductive tract secretion, and the function of the disabling factor is relieved. Only then can the sperm have the real fertilization ability, which is sperm capacitation.
“Capacity” is not to obtain energy, but to obtain the ability to fertilize. Capacitation refers to the ability of sperm to penetrate the zona pellucida, which is an important stage that sperm must go through before fertilization. With the capacitation of the sperm, the oxygen consumption increases, the movement of the sperm is accelerated, and the sperm quickly swims to the egg, and finally the sperm-egg combination is realized. Recently, Japanese scientists have made an exciting breakthrough in the study of the mechanism of calcium ions in “capacitation” and “super-activation exercise” (Protein defect leaves sperm chasing their tails. ScienceDaily, 2 December 2019).
As the second messenger of cells, calcium ions play an important role in regulating the permeability of cell membranes and the metabolism of substances in cells. The concentration of calcium ions in seminal plasma plays an important role in sperm movement. Low calcium is not conducive to sperm motility. Studies have found that a large amount of calcium ion flow occurs during sperm capacitation. At the same time, calcium ions are a necessary condition for sperm hyperactive movement. If the hyperactive sperm is transferred to calcium-free medium for 30-60 minutes, the hyperactive motion will stop, but if calcium ions are added at this time, the hyperactive motion will resume. Calcium ions can enhance the beating amplitude of the flagella of sperm, and the level of calcium ions in the cell is directly related to the hyper-activated movement.
Scientists already know that an electrical signal sensor protein called VSP is expressed in sperm of many animals, but the actual physiological role of this protein is still unclear. Japanese researchers have noticed that the ability of sperm lacking VSP to fertilize eggs in vitro is greatly reduced. Close inspection revealed that very few sperm actually reached their destination. Defects in sperm motility indicate a problem with the flagella, prompting researchers to examine these structures in more detail. Studies have found that VSP plays a major role in the regulation of calcium channels and ultimately affects sperm motility. The researchers proposed a mechanism: VSP is responsible for the polarization distribution of PIP2 in the flagella, and PIP2 activates potassium ion channels, which indirectly leads to the local influx of calcium ions, thereby enhancing sperm motility.
This study revealed the mechanism by which calcium ions regulate sperm motility and insemination. The researchers said, “Our findings will lead to the development of fertility treatments that can improve sperm motility and increase the chance of fertilization.” We know that middle-aged and elderly people have insufficient calcium absorption capacity and decreased calcium levels in the body due to decreased liver and kidney function. This should be one of the reasons for the decline in sexual desire and fertility in middle-aged and elderly people. It also suggests that men who want to have children should take calcium supplements to effectively improve their fertility.
