Intrauterine proximity to male fetuses predetermines level of epidermal growth factor in submandibular glands of adult female mice.

Morphological, behavioral, and physiological masculinization of adult female mice that developed in utero between two male fetuses (2M females) has been previously attributed to the significantly higher concentration of testosterone in their fetal blood and amniotic fluid than that in female mice which had not been contiguous to males in utero (0M females). Serum testosterone levels of adult 2M and 0M females are not significantly different. To determine whether exposure of fetuses to different levels of testosterone during prenatal development alters adult biochemical parameters of a system responsive to testosterone, the level of epidermal growth factor (EGF) was measured by radioreceptor assay in the submandibular glands of adult CF-1 mice of known intrauterine position. The concentration of EGF was significantly higher (P less than 0.05) in the glands of 2M females (mean +/- SEM, 0.36 +/- 0.14 nmol/mg dry wt of tissue; n = 6) than that in 0M females (0.05 +/- 0.00 nmol/mg dry wt; n = 8). In contrast, EGF concentration did not differ significantly between the glands of 2M and 0M males (0.51 +/- 0.01 and 1.10 +/- 0.42 nmol/mg dry wt, respectively). EGF levels were also determined in the submandibular glands from adult animals of unknown intrauterine position which were gonadectomized and then treated with testosterone and estradiol. The concentrations of EGF in the glands of gonadectomized males and females were similar (0.13 +/- 0.01 and 0.23 +/- 0.09 nmol/mg dry wt, respectively). However, there was a significant difference in response to hormonal administration between males and females. The response of females exceeded that of males at 400 and 800 micrograms testosterone/day. These results suggest that the hormonal environment of a fetus, specifically modification of the fetal environment by the production of hormones from adjacent fetuses, is a major factor in the adult expression of testosterone-responsive proteins such as EGF.