Growth of the penis at sexual maturation is under the control of androgens, but growth ceases as the organ reaches adult size despite continued high levels of circulating androgen. Previous studies have shown that the cessation of penile growth is associated with a decrease in the quantity of androgen receptor, as detected by ligand binding and immunological methods. In the current studies we demonstrate that the decreased androgen receptor levels correlate with a decrease in androgen receptor mRNA content in the penile corpus and os, but not in the glans penis. These findings suggest that modulation of androgen receptor mRNA levels in the body of the penis may be important to the control of androgen-dependent growth in the tissue, and that the control of androgen receptor mRNA levels differs among the different cell types that comprise the penis. To explore the mechanisms controlling androgen receptor expression, we examined the transcription initiation site of the rat androgen receptor gene in ventral prostate and in three compartments of the penis: The corpus, the urethra, and the glans penis. The same promoter is employed in all preparations, suggesting that the different patterns of androgen receptor mRNA expression in these tissues with age are controlled by factors that modulate the activity of the same promoter.
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