Cigarette smoking impairs sperm chromosome function
MedWire News: Men who smoke cigarettes have lower protamine 2 levels than nonsmokers, leading researchers to suggest this could account for infertility in some men.
"Protamine content is necessary for proper sperm chromatin condensation and subsequent male fertility," say Mohammed Hammadeh, from the University of the Saarland in Germany, and colleagues.
The positively charged protamines allow the neutralization of DNA in the sperm, protecting it from damaging oxidative stress that is associated with low fertilization rates, impaired preimplantation development, increased miscarriage rates, and an elevated incidence of disease in the offspring.
Protamine 2 levels were a statistically significant 14 percent lower in the sperm of 53 heavy smokers (defined as more than 20 cigarettes per day) compared with 63 nonsmokers, at 334.7 ng/million versus 338.8 ng/million.
Furthermore, markers of oxidative stress (malondialdehyde, reactive oxygen species, and 8-Hydroxy-2-deoxyguanosine) were significantly higher in the seminal plasma of a subsample of 31 of the heavy smokers compared with 32 of the nonsmokers.
"These results suggest that induced oxidative stress by cigarette smoking may have a significant inverse effect on chromatin condensation by disrupting protamine 2," concluded Hammadeh.
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By Sarah Guy