RNA polymerase activities in isolated nuclei of guinea pig seminal vesicle epithelium: influence of castration and androgen administration

The effects of androgen on the transcription of specific genes in guinea pig seminal vesicle epithelium

Steroid hormones have been shown to have highly differential effects on the expression of abundant cell-specific protein genes in a multitude of model tissues. In rat seminal vesicle, for example, DNA clones representing two major secretory protein genes have been used to show that both of the genes are differentially regulated by androgen. In this paper, we have examined the effects of androgen on the transcription of two major secretory protein genes in guinea pig seminal vesicle epithelium. Nuclear run-off experiments were used to show that castration of the adult resulted in a 3-fold decrease in total transcription activity. Surprisingly, the decrease in total transcriptional activity was not reflected in a differential decrease in the transcriptional activity of the two major secretory protein genes. When the effects of castration on the transcriptional activity of the major secretory protein genes were compared to the effects on other genes, it was found that the transcriptional activity of each gene examined was decreased by the same magnitude as the major secretory protein genes. Similarly, the transcriptional activity of every gene examined increased by the same magnitude as the major secretory protein genes during hormone repletion of the castrated adult. Thus, in contrast to the differential effects of steroids on the transcription of abundant cell-specific proteins in many other steroid-dependent tissues, the transcription of major secretory proteins in guinea pig seminal vesicle epithelium appears to be regulated in parallel with many other genes. The generalized effects of androgen on transcriptional activity could account for the generalized effects of androgen on seminal vesicle epithelial cell structure and function.

Nuclear acceptor sites for androgen-receptor complexes in seminal-vesicle epithelium

An assay method in vitro was developed and applied to quantify acceptor binding of steroid-receptor complexes in nuclei from isolated epithelium of guinea-pig seminal vesicle. Steroid-receptor complex prepared from 1-day-castrated animals was incubated with purified nuclei from 1-28 day-castrated animals in a medium containing 0.15 M-KCl. Free and bound steroid-receptor complexes were measured and the data were submitted to Scatchard analysis. With nuclei from 1-day-castrated animals the Kd for binding of cytosolic [3H]dihydrotestosterone-receptor complexes was found to be 0.83 X 10(-10) M and the capacity for binding was 0.35 pmol/mg of nuclear DNA. Scatchard analysis consistently disclosed only a single line of constant slope and gave the same kinetic constants for nuclei obtained from animals castrated up to 28 days before assay. Administration of 2 mg of dihydrotestosterone, 3 alpha-androstanediol or androsterone or 100 microgram of oestradiol-17 beta 1 h before killing of the 1-day-castrated animals that provided the nuclei resulted in a significant decrease in nuclear acceptor binding of the steroid-receptor complex compared with untreated animals. Thus our assay method disclosed nuclear acceptor sites that may be involved in responses to androgens (and oestrogens) in vivo. We conclude that there is a class of nuclear accept or sites of high affinity and limited capacity that may be occupied by steroid-receptor complexes in vivo.