Reproductive and endocrine function in rams exposed to the organochlorine pesticides lindane and pentachlorophenol from conception

There is controversy over the potential endocrine modulating influence of p esticides, particularly during sensitive phases of development. In this stu dy, ram lambs were exposed to lindane and pentachlorophenol from conception to necropsy at 28 weeks of age. The rams (and their mothers) were given un treated feed (n = 7) or feed treated with 1 mg kg(-1) body weight per day o f lindane (n = 12) or pentachlorophenol (n = 5). Semen was collected from 1 9 weeks onwards and reproductive behaviour was tested at 26 weeks. Serum wa s collected every 2 weeks and at 27 weeks every 15 min for 6 h during both day and night, and for Ih before and 5 h after stimulation with GnRH, adren ocorticotrophic hormone and thyroid-stimulating hormone. The pesticides did not affect body weight and ejaculate characteristics, or cause overt toxic ity. In pentachlorophenol-treated rams, scrotal circumference was increased . However, seminiferous tubule atrophy was more severe and epididymal sperm density was reduced in comparison with untreated rams at necropsy (P < 0.0 5). Thyroxine concentrations were lower in pentachlorophenol-treated rams t han in untreated rams (P < 0.05). However, after thyroid-stimulating hormon e treatment, the thyroxine response was unaltered. Reproductive behaviour w as reduced in Lindane-treated rams compared with control rams (P < 0.05). S erum LH and oestradiol concentrations during reproductive development, LH p ulse frequency at 27 weeks and testosterone secretion after GnRH treatment were lower in lindane-treated rams than in untreated rams (P < 0.05). In su mmary, the effects of pentachlorophenol on the testis may be linked to a de crease in thyroxine concentrations, and reduced reproductive behaviour in l indane-treated rams may be related to decreased LH, oestradiol and testoste rone concentrations.