Evaluation of spermatogenesis and sperm quality in the rat following acute inhalation exposure to methyl bromide.

Methyl chloride (MeCl) and methyl bromide (MeBr) have similar target organ specificities in the male F-344 rat, and MeCl is a known reproductive toxicant in that species. Recently, both acute and subchronic inhalation exposures to MeBr were found to produce varying degrees of testicular alteration (S.L. Eustis, S.B. Haber, R.T. Drew, and R.S.H. Yang, 1986, Toxicologist, 6, 54; N. Kato, S. Morinobu, and S. Ishizu, 1986, Ind. Health, 24, 87-103; M.E. Hurtt, K.T. Morgan, and P.K. Working, 1987, Fundam. Appl. Toxicol., 9, 352-365). The present study examined the reproductive effects of MeBr in the male F-344 rat. Adult males (11-13 weeks) were exposed by inhalation to 0 or 200 ppm MeBr 6 hr/day for 5 days (first day of exposure = Day 1). Ten animals from each group were anesthetized with pentobarbital and terminated on Days 1, 3, 5, and 8. Additionally, five males from each group were killed on Days 6, 10, 17, 24, 38, 52, and 73. Plasma testosterone concentration was reduced during and immediately following exposure (Days 1, 3, 5, and 6), but returned to control levels by Day 8. Nonprotein sulfhydryl (NPSH) content of the liver and testis was reduced during exposure but returned to control levels by Day 8 (3 days postexposure). No other reproductive indices, including testis weight, daily sperm production, cauda epididymal sperm count, sperm morphology, percentage motile sperm, linear sperm velocity, and epididymal and testicular histology, were affected by MeBr exposure at any time point examined. Thus, although MeBr causes a transient decrease in plasma testosterone and testicular NPSH concentrations during acute exposure, it has no lasting effect on sperm quality or spermatogenesis in the F-344 rat.