Effects of paint thinner inhalation on serum testosterone synthesis and secretion were investigated in the male rat. A control group inhaled normal air ventilation. The remaining animals were divided into three groups and exposed to paint thinner in a glassy cage for 15 and 30 days. A group of animals was allowed to recover for 15 day after 30 days of exposure. Toluene concentration (the largest constituent in thinner, 66%) was set at 1500 ppm in the inhalation air. At the end, all animals were decapitated and blood samples obtained. Testes were removed and weighed out. Serum total testosterone levels were determined by chemiluminescence enzyme immunoassay. Testicular tissue specimens were processed for semi quantitative evaluation of immunohistochemical testosterone staining. Intensity of immunostaining was evaluated on a scale between 0 (no staining), 1 (minimal), 2 (mild), 3 (moderate) and 4 (strong staining). Serum testosterone levels (ng) were decreased by 15 (3.31±0.61) and 30 (1.17±0.54, p<0.02) days thinner inhalation compared to the controls (3.91±1.03). Reduced testosterone values were significantly elevated after 15 days of recovery period (3.77±1.1) compared to 30 day exposure group (p<0.05). Immunohistochemical testosterone staining of the cytoplasm of Leydig cells was moderate (3+) and mild (2+) in 15 and 30 days thinner inhalation groups, respectively. Strong staining (4+) was restored following the recovery period. Testicular weight was significantly reduced in all test groups compared to the control values (p<0.01). The present findings suggest that paint thinner inhalation inhibits testosterone secretion by a direct effect on the Leydig cells in a reversible manner.
22 - 24 Mar 2004
British Endocrine Societies