MALE REPRODUCTIVE EFFECTS OF LEAD, INCLUDING SPECIES EXTRAPOLATION FOR THE RABBIT MODEL

The effects of elevated blood lead on semen quality were evaluated in the rabbit model and compared to published effects in humans. Mature, male rabbits were given lead acetate by subcutaneous injection in the dose range of 0 to 3.85 mg/kg on a Monday-Wednesday-Friday basis. In e ach of eight treatment groups, a dosing regimen was developed to produ ce blood lead levels of 0, 20, 40, 50, 70, 80, 90, and 110 mu g/dL. A 5-week pre-exposure period was followed by a 15-week exposure testing period allowing for response through six cycles of the seminiferous ep ithelium, Semen analyses revealed that increased blood lead levels wer e associated with adverse changes in the sperm count, ejaculate volume , percent motile sperm, swimming velocities, and morphology. Hormonal responses were minimal. Testicular pathology revealed a dose-dependent inhibition of spermiation, For six measures of semen quality, thresho ld estimates ranged from 16 to 24 mu g/dL. Using the species extrapola tion factor derived in this study, a rabbit dose would have to be divi ded by 1.56 to obtain the equivalent human dose for an equal percentag e decrease in sperm concentration; however, rabbits are 3.75 more sens itive in terms of absolute decrease in sperm count for a given blood l ead level. Published by Elsevier Science Inc.