Figure 3.

Probable mechanism of association of radiation-induced ROS with hypogonadism and ED. Nonionizing radiations damage the Leydig cells, which reduces testosterone synthesis and subsequent inhibition of spermatozoa. Such radiations negatively affect sperm parameters, including count, motility, morphology, viability and motility. Nonionizing radiations also stimulate NO activity, which along with ROS, brings about lipid peroxidation and damage to testicular tissues. These tissues are also damaged by apoptosis mediated by elevated ROS levels. Nonionizing radiation-induced ROS further causes DNA damage and decreases the concentration of histone kinase along with a reduction of SOD and glutathione peroxidase activity. Whereas ionizing radiations cause a decline in testosterone production by damaging Leydig cells and by inhibiting the activity of steroidogenic enzymes. Such radiations enhance LDH activity, which results in cellular damage. Damage to the penile smooth muscles and reduced ICP may cause ED. ED is also caused by decreased cGMP levels and damage to the corpus cavernosum, which are brought about by ionizing radiation-induced oxidative stress. Red arrows represent the increase and decrease of the respective substances and sperm parameters beyond harmful levels. (NO: nitric oxide, SOD: superoxide dismutase, LDH: lactate dehydrogenase, ICP: intracavernosal pressure, ODO: oxadiazoloquinoxalin-1-one, cGMP: cyclic guanosine monophosphate, ED: erectile dysfunction, ROS: reactive oxygen species).