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The controversial pesticide endosulfan, widely used by Indian farmers, not only induces male infertility but also exerts damage on the liver and lungs, says a team of researchers from the Indian Institute of Science (IISc) in Bengaluru who have obtained conclusive evidence from animal studies.
Sathees C. Raghavan, associate professor in the department of biochemistry, and Robin Sebastian, a research scholar, recorded significant cell death in the testes, the organ that produces sperm, in mice that were exposed to endosulfan.
The research, published recently in the journal "Cell Death Discovery," found that endosulfan treatment significantly affected the complete cycle of sperm formation, causing the testes to waste away (testicular atrophy).
In Kasargod district in northern Kerala, endosulfan was regularly sprayed on cashew plantations for over two decades starting in 1976. Subsequently, inhabitants started developing diseases like cancer, birth defects and deformations which were thought to be due to excessive endosulfan use.
"As northern Keralites, we always had first-hand experience on the political and social phases of the endosulfan issue and we were quite intrigued to test and methodologically evaluate the mechanistic aspects of endosulfan action", Raghavan told IANS.
Raghavan recently spoke at the session on "Genetic dissection of complex diseases" during the 103rd Indian Science Congress in Bengaluru where he shared the study findings with the gathering at a packed auditorium.
The precise mechanism by which endosulfan exerts its effect, however, remains largely unclear. For the study carried out in mice, the researchers chose an endosulfan concentration of 3mg/kg of body weight -- comparable to what has been detected in the blood serum of human subjects living in areas of endosulfan exposure.
The mice were treated with four doses of endosulfan, spanning eight days.
Liver function tests showed decreased levels of essential enzymes (as compared to untreated control) and tissue analyses after first day of treatment completion showed that liver, testes and lungs were maximally affected upon endosulfan treatment whereas brain, intestine and kidney showed no sign of toxicity.
The levels of red blood cells and platelets also went down as opposed to normal levels, the report said.
"Immediately after endosulfan exposure, the DNA integrity of the sperm was significantly perturbed," Raghavan said. "This effect was transient and found to be mediated through high levels of particular molecules called Reactive Oxygen Species levels, which may interact with and damage the genetic material DNA, causing genomic instability within sperms," he said.
Although the morphology of sperms remained normal, there was a dramatic reduction in sperm count and motility after the endosulfan treatment. To test the implications of this effect on fertility in mice, the researchers conducted mating experiments and found that about a third of the males treated with endosulfan were infertile.
Raghavan said that because of the growing concerns about health hazards of endosulfan, "the molecular insights behind changes induced by endosulfan" are currently under investigation in his laboratory.
"The study could be further extended to other types of pesticides with possible side effects in health. This would be a first step towards a more rationalised usage of pesticides," he noted.
(K. S. Jayaraman can be contacted at firstname.lastname@example.org)