Androgen receptor in genital tubercle of rabbit fetuses and newborns. Ontogeny and properties

Ontogeny of androgen receptor and disruption of its mRNA expression by exogenous estrogens during morphogenesis of the genital tubercle

PURPOSE

The ontogeny of androgen receptor expression in male and female mouse genital tubercles, and the effects of in utero ethinyl estradiol exposure on androgen receptor mRNA expression in the hypospadias model were studied.

MATERIALS AND METHODS

Androgen receptor mRNA expression was measured in mouse genital tubercles from fetuses and pups collected on gestational days 12, 14, 16 and 18, and from newborns using immunohistochemistry and real-time quantitative polymerase chain reaction. Pregnant dams were exposed to ethinyl estradiol or corn oil as controls from gestational days 12 to 17. Genital tubercles of gestational day 19 fetuses were then examined by further quantitative polymerase chain reaction analysis after identification of the seam area using a dissecting microscope to diagnose hypospadias in males.

RESULTS

Androgen receptor protein was detected in genital tubercles by gestational day 14. Androgen receptor mRNA expression increased gradually in each sex during normal development. However, female genital tubercles expressed a higher level of androgen receptor mRNA throughout development compared to male genital tubercles (p <0.0001). In utero ethinyl estradiol exposure led to a 5.4 and 4.5-fold increase in androgen receptor mRNA in the genital tubercles of female and male embryos (p = 0.004 and 0.001, respectively). Hypospadiac male genital tubercles showed increased androgen receptor mRNA expression compared to control males (p = 0.006). Levels in hypospadiac males did not differ from those in control females but they were less than those in ethinyl estradiol treated females (p >0.05 and 0.01, respectively).

CONCLUSIONS

Androgen receptor protein is expressed abundantly in male and female genital tubercles. Androgen receptor mRNA levels are higher in female than in male genital tubercles through development and they increase in response to in utero ethinyl estradiol exposure with ethinyl estradiol treated females having the highest levels of expression, followed by ethinyl estradiol treated hypospadiac males. We infer that higher estrogen in genital tubercles results in a physiological response of increased androgen receptor mRNA expression. We found no direct association between changes in androgen receptor mRNA expression and the presence or absence of hypospadias in males, suggesting that alterations in the expression of proteins other than or in addition to androgen receptor result in anomalous urethral development. This finding supports the idea that the etiology of hypospadias is multifactorial in origin.

Age-related changes in the concentration of cytosolic androgen receptors in the epididymis, vas deferens and seminal vesicle of maturing male mice

In this study, changes in the number of androgen binding sites that occur in cytosols of epididymis, vas deferens and seminal vesicle of mice from 10 to 90 days of age are described. Specific saturable binding of [3H]R-1881 by cytosols of the three organs at all time points studied and age-related differences in the number of binding sites measured were observed. Cytosolic androgen receptor levels in all three organs studied were found to decrease with increasing age, regardless of whether the binding was expressed relative to weight of tissue, cytosolic protein or cellular DNA. The most pronounced change in androgen receptor levels (from 442 to 50 fmol/mg protein) was observed in the epididymis between 10 and 30 days of age. In these three organs there was no significant correlation between androgen (testosterone + dihydrotestosterone) levels and the concentration of androgen binding sites.