Student Research: Timothy G. Ewers

, , 1993
Faculty Advisor: Elaine M. Faustman

Examination of the effects of Lead on Spermatogenesis and Sperm Chromatin Structure in Rats


Abstract

Two separate studies were conducted in which two different straines of rates were exposed to lead in their drinking water. In the preliminary study, late-adolescent Fischer-344 male rats were exposed to 0, 366, or 732 ppm lead acetate orally for up to 10 weeks. Blood-lead levels, determined by atomic absorbance spectrophotometry, were below detection (<5 ug/dl) in the control animals and were maintained between 20 and 82 ug/dl in the exposed animals. No effect on sperm chromatin structure was observed by using the Sperm Chromatin Structure Assay (SCSA). Howver, significant exposure-repated effects were observed by flow cytometry in the proportions of testicular germ cells. Results indicate stage-specific effects of lead toxicity on spermatogenesis. Specifically, decreases in the proportions of tetrploid germ cells and elongating spermatids and increases in the proportions of round spermatids were observed with lead treatment. In the second study, sexually mature Wistar rats were exposed to 0, 100, 500, 1000 or 3000 ppm lead acetate. Blood-lead levels varied in statistically-significant and exposure-related manner from below detection to 55 ug/dl. No effects were observed in the proportions of testicular gems cells from any animals exposed to lead for 2, 5 or 10 weeks. No effects were observed by the SCSA in cauda epididymal sperm from rats exposed to lead for 10 weeks. Factors contributing to the differences in the responses between the two studies include: animal strain, age at exposure initiation and the level of lead exposure.