To study the relationship between the sperm motility and the energy metabolism in human sperm exposed to extremely low frequency electromagnetic fields. Moreover, the energy contribution of mitochondrial respiration and glycolysis to the enhancement of sperm motility induced by extremely low frequency electromagnetic fields was also assessed. In addition, the same evaluations were carried out when glycolytic (glucose) or mitochondrial (lactate and pyruvate) substrates were added and when glycolytic or mitochondrial metabolism were inhibited.
A previous study showed that extremely low frequency electromagnetic fields with a square wave form of 5 mT intensity and 50 Hz frequency was able to promote human sperm motility (see Iorio et al. 2007).
To inhibit mitochondrial activity, the spermatozoa were incubated with medium containing carbamoyl cyanide m-chlorophenylhydrazone (CICCP). To inhibit glycolytic metabolism, spermatozoa were incubated in medium containing 2-deoxy-D-glucose.
All experiments were replicated at least five times.
|Exposure duration||continuous for 1 h, 2 hr or 3 hr|
|Duty cycle||50 %|
|Setup||200 mm long solenoid with a diameter of 160 mm amd 511 turns placed in an incubator with a constant temperature of 37° C, 100 % relative humidity and an atmosphere of 95 % air and 5 % CO2; constant magnetic field in a 10 mm long cylindrical region with a diameter of 10 mm inside the solenoid; samples placed in the core of the solenoid|
|Sham exposure||A sham exposure was conducted.|
|magnetic flux density||5 mT||-||measured and calculated||-||-|
Extremely low frequency electromagnetic field exposure resulted in a progressive and significant increase of mitochondrial membrane potential and levels of ATP, ADP and NAD+ that was associated with a progressive and significant increase in the sperm kinematic parameters. No significant effects were detected on other parameters such as ATP/ADP ratio and energy charge. Thus, the data showed that the stimulatory effect exerted by the extremely low frequency electromagnetic field on sperm motility characteristics was associated with increases in mitochondrial membrane potential and levels of ATP, ADP and NAD+, suggesting an important role of mitochondrial metabolism in the energy production required for flagellar movement.
When mitochondrial activity was inhibited and glucose was the only source of energy in the medium (to promote glycolysis), the values of energy parameters and sperm motility in sperms exposed to extremely low frequency electromagnetic fields did not change (compared with sham exposed sperm samples). Thus glycolysis was not involved in mediating magnetic fields stimulatory effect on sperm motility.
By contrast, when pyruvate and lactate (as mitochondrial substrates) were provided instead of glucose and under inhibition of glycolysis by 2-deoxy-D-glucose, the energy status and sperm motility increased significantly in electromagnetic field exposed sperm samples.
In conclusion, the data revealed a key role of mitochondria in mediating the electromagnetic field stimulatory effect on human sperm motility.