Effects of the chlorinated hydrocarbon (dieldrin) on testicular morphology and endocrinology in the male rat

Abstract

Experimental studies portray that a large number of chemicals namely environmental and industrial pollutants affect the male reproductive system. Reproductive toxicants exert their effect at different stages of the male reproductive system with some influencing the central and the autonomic nervous systems and lor the hypothalamic pituitary - testicular axis causing reproductive dysfunction. This study investigated the biological effects of parenteral and oral administration of dieldrin on reproductive function of mature male rats. In another set of experiments the effect of parenteral administration of dieldrin on plasma testosterone levels and histology of the testicular tissues of neonatal male rats were investigated. Dieldrin was injected subcutaneously to mature male rats (Spraque- Dawley) every other day for 20 days. Experimental rats received dieldrin at a dose of either 5mg (n=10) or 10mg (n=IO) Ikg body weight in corn oil while the control group (n=IO) was treated with the vehicle (corn oil). All animals were killed at the end of the experiment and blood samples were assayed for testosterone and luteinizing hormone (LH). Testicular tissues from one testis of each rat were processed for histological examination and Leydig cells were isolated from the other testis and incubated with LH to investigate testosterone production in vitro. Dieldrin depressed plasma testosterone levels at a dose of 10mg/kgbody weight and depressed plasma LH at both 5 and lOmg/kg-body weight (P<0.05). Also, dieldrin significantly suppressed the production of testosterone by Leydig cells ill vitro (P<O.OOI). In another set of experiments, mature male rats were fed on dieldrin spiked diet ad-libitum for 20 days. Experimental rats received dieldrin at a dose of either Smg (n=10) or 10mg (n=10) /kg- body weight while the control group received a dieldrin free diet. All animals were killed at the end of the experiment and blood samples were assayed for testosterone and LH while testicular tissues were processed for histological examination. There were no significant differences (P>O.OS) in plasma testosterone and LH concentrations between rats fed dieldrin spiked and dieldrin free diets. In the two experiments, the histology of the testes and epididymis was not altered in dieldrin treated rats. In another experiment dieldrin was subcuteneously injected to one to two days old male rats at every other day interval for 10 days. Test animals received dieldrin at a dose of either Smg (n=12) or 10mg (n=12)/rat in O.lmL of vehicle while the control group (n=12) received 0.1mL of corn oil. At the end of the experiment all rats were killed and blood samples were assayed for plasma testosterone and testicular tissues were processed for histological examination. Dieldrin significantly suppressed testosterone concentration in plasma in a dose-related manner (P<O.OS). In the treated animals the histology of the testes and epididymis was not altered. In the last experiment mature female rats of proven fertility (multipara) were allowed to mate with male rats treated with either vehicle or dieldrin. The number of pregnant females and their subsequent litter sizes were recorded. There was no significant differences (P>O.OS) in the number of pregnant females and the subsequent litter sizes between females mated to males treated with either corn oil or dieldrin. In conclusion, these results indicate that dieldrin has less affects on the testosterone and LH concentrations in plasma when given orally than when given parenterally to mature rats at either Smg or 10mg/kg-body weight doses. Also in addition, these results indicate that dieldrin decreases plasma concentration of testosterone in male neonate rats. Lastly, it was shown that dieldrin when administered at doses Sand 10mg/ bwt has no short-term effects on the fertility and histology of the testicular tissues of treated rats.