Heavy oil fraction induces the dysplastic sperm in male mouse.

Heavy oil is one of the most serious pollutants in marine ecosystem. The poisonous influences of the chemical substances contained in heavy oil on many kinds of marine organisms are widely studied. However, the influence of the chemical compounds in heavy oil on our health has not been cleared yet. In order to reveal the poisonous influences of these chemical compounds on mammalian reproductive system, water-soluble fraction (WSF) extracted from heavy oil was administrated to mice for 2 weeks. WSF-administrated mice were crossed with either WSF- or distilled water-administrated group for mating experiment. When WSF-administrated male mice were used as a father, it reduced not only mating ratio, but also neonatal male ratio. The numbers of sperms of WSF-administrated male mice were decreased. In addition, abnormality of sperms such as bent or twisted tail was increased approximately 6-fold by WSF intake. The level of testosterone in serum from WSF-administrated mice was lower than that from control mice. Testosterone is the most important for the spermatogenesis in vertebrate. It is supposed from these findings, the decrease in the number of sperms may relate with the reduction of sex hormone level in serum. It is suggested from these results that the chemical substances in WSF affected the sperm function in reproductive system of male mice.