Gonadal effects of fetal exposure to the azo dye Congo red in mice: Infertility in female but not male offspring

The present study describes the relationship between gonadal agenesis and fertility in male and female mice exposed in utero to the diazo dye Congo red (CR). Maternal CR treatment inhibited testicular and ovarian function in the offspring after oral administration of 1 or 0.5 g/kg/day on Gestational Days 8–12. The testes of male offspring from CR-exposed dams were small in size and contained hypospermatogenic seminiferous tubules. However, despite the fact that testis weight was reduced by more than 70% in some males, they displayed normal levels of fertility when mated to untreated females for over 10 months. In contrast, female offspring from CR-exposed dams produced only about half as many litters and pups as the control pairs did under longterm mating conditions. Histological examination of the ovaries revealed that subfertility was correlated with ovarian atrophy. Females lacking maturing follicles were considerably less productive (1.3 litters and 11.5 pups) than treated females with histologically normal ovaries (7.1 litters and 78.1 pups). In summary, prenatal exposure to the dye CR affects the gonads of both male and female offspring, but only the female offspring display reduced fertility.