Relative importance of prenatal and postnatal androgen action in determining growth of the penis and anogenital distance in the rat before, during and after puberty.

Experimental animal studies show that measurement of anogenital distance (AGD) and/or penis length may provide lifelong 'read-outs' of foetal androgen exposure during the masculinization programming window (MPW). However, variation in postnatal androgen exposure may complicate interpretation of such measurements. This is important to clarify if such measurements are to be applied to humans. The present aim was to evaluate effects of prenatal and/or postnatal manipulation of androgen production/action on growth of AGD and the penis in rats. Pregnant rats were treated daily before (e13.5-e21.5) and after birth (postnatal days 1-15) with either vehicle, 500 mg/kg di(n-butyl) phthalate (DBP) or 100 mg/kg flutamide (postnatal only) in prenatal + postnatal treatment combinations (N = 6 treatment combinations); DBP impairs androgen production whereas flutamide impairs androgen action. Male offspring were killed on postnatal day 8 (prepuberty), 25 (early puberty) or 90 (adulthood) when AGD was measured, the penis dissected out and its weight and length measured; plasma testosterone and ventral prostate weight were measured at day 90 to assess endogenous androgen exposure. In controls, penis length, girth and AGD increased 2.2-, 5.3-and 5.9-fold respectively from day 8 to day 90. Significant inhibition of penis growth and final length and girth was induced by treatments that inhibited postnatal androgen action. Conversely, growth and ultimate (adult) AGD was inhibited by prenatal inhibition of androgen production whereas postnatal androgen inhibition had negligible effect. Nevertheless, AGD and penis length were highly correlated at every age (R(2) > 0.33; p < 0.0001). However, altered endogenous androgen exposure may confound interpretation of changes in adults exposed prenatally/postnatally to DBP/flutamide. We conclude that AGD provides a lifelong guide to prenatal androgen exposure (in the MPW) whereas penis size reflects both prenatal + postnatal androgen exposure. At the group treatment level, prepubertal measurement of either AGD or penis size accurately predicts their size in adulthood.

Androgen action in the masculinization programming window and development of male reproductive organs.

We have shown previously that deficient androgen action within a masculinization programming window (MPW; e15.5-e18.5 in rats) is important in the origin of male reproductive disorders and in programming male reproductive organ size, but that androgen action postnatally may be important to achieve this size. To further investigate importance of the MPW, we used two rat models, in which foetal androgen production or action was impaired during the MPW by exposing in utero to either di(n-butyl) phthalate (DBP) or to flutamide. Reduced anogenital distance (AGD) was used as a monitor of androgen production/action during the MPW. Offspring were evaluated in early puberty (Pnd25) to establish if reproductive organ size was altered. The testes, penis, ventral prostate (VP) and seminal vesicles (SV) were weighed and penis length measured. Both DBP and flutamide exposure in the MPW significantly reduced penis, VP and SV size along with AGD at Pnd25; AGD and organ size were highly correlated. In DBP-, but not flutamide-, exposed animals, testis weight was also reduced and correlated with AGD. Intratesticular testosterone was also measured in control and DBP-exposed males during (e17.5) or after (e21.5) the MPW and related to AGD at e21.5. To evaluate the importance of postnatal androgen action in reproductive organ growth, the effect of combinations of prenatal and postnatal maternal treatments on AGD and penis size at Pnd25 was evaluated. In prenatally DBP-exposed animals, further postnatal exposure to either DBP or flutamide significantly reduced AGD and penis size in comparison with prenatal DBP exposure alone. In comparison, rats exposed postnatally to testosterone propionate after prenatal vehicle-exposure showed considerable increase in these parameters vs. controls. In conclusion, we show that the size of all male reproductive organs is programmed by androgen exposure in the MPW, but that growth towards this size is dependent on androgen action postnatally.