Hormonal Regulation of Protein Synthesis in Rat Ventral Prostate

Abstract

SHOGO ICHII, MASAO IZAWA AND NORIKO MURAKAMI SynopsisTo elucidate details of hormonal regulation mechanism in rat ventral prostate, synthesis of RNAs that contain polyadenylate sequences, polyribosomal sedimentation profile, ribosomal capacity of 3H-Met-tRNA binding, ribosomal initiation factor activity and the rate of polypeptide chain elongation were examined in the ventral prostate from control and castrated animals. The following results were obtained ;1) The concentration of RNAs that contain polyadenylate sequences in cytoplasm of castrated rats was markedly decreased, while the content in nuclear fraction was not influenced significantly by castration. 2) Polyribosomes disappeared quite rapidly after castration and were completely restored 48 hr after testosterone administration. 3) Ribosomal binding capacity with 3H -Met-tRNA and ribosomal initiation factor activity were also reduced significantly.Testosterone treatment of castrated animals completely abolished the effect of castration on ribosomal binding capacity with 3H-Met-tRNA and initiation factor activity. 4) A relatively small effect of castration on the relative rate of polypeptide chain elongation in rat ventral prostates was observed. These results may indicate that the regulation of protein synthesis exerted by testosterone in rat ventral prostates is not restricted at the step of the transcription of mRNA.

Nuclei and DNA-binding form of the steroid receptor complex in the liver and the ventral prostate of rats.

“…According to this result, the hormone-receptor complex which binds to DNA and nuclei would not be required for the action of dihydrotestosterone on the rat ventral prostate. Lack of tissue specificity in the binding of hormone-receptor complex to isolated nuclei has been reported Chamness et al, 1973;Ichii, 1975) and the high affinity and saturable binding of dexamethasone-receptor complex to liver nuclei has not been observed in the in vitro binding experiment (Ichii, et al, 1977). On the other hand, the interaction of glucocorticoids and liver cytosol with liver nuclei was postulated to be tissue specific (Milgrom and Atiger, 1975) and a specific high affinity binding of steroid-receptor complexes has also been reported (Kalimi et al, 1973Chatkoff and Julian, 1973).…”

Distribution of Acceptor Sites for Androgen-Receptor Complexes Between Transcriptionally Active and Inactive Fractions of Rat Ventral Prostate Chromatin

“…The resultant DHT-receptor complexes become translocated to the nucleus where they are apportioned to various regions of nuclear chromatin defined by the presence of specific acceptor sites. Although effects of androgens at extranuclear sites cannot be excluded (Ichii, Izawa & Murakami, 1974;Liang & Liao, 1975), alterations in transcriptional events brought about by the arrival of DHT-receptor complexes at the acceptor sites seem to reflect the major area of influence. Prostate chromatin responds to this occurrence with alterations in the activity of RNA polymerase (EC 2.7.7.6, nucleosidetriphosphate : RNA nucleotidyltransferase) (Davies & Griffiths, 1974;Hu, Loor & Wang, 1975;Mainwaring & Jones, 1975; Thomas, , followed by increased synthesis of various essential cellular macromolecules (see Mainwaring, 1977).…”

Measurement of Free and Occupied Cytoplasmic and Nuclear Androgen Receptor Sites in Rat Ventral Prostate Gland

“…The distribution of androgen receptors in prostatic cytoplasm and nucleus (King «fe Mainwaring, 1974;Liao «fe Liang, 1974;Bruchovsky, Lesser, Van Doom «fe Craven, 1975a), and their postulated involvement in transcriptional (Davies «fe Griffiths, 1973Griffiths, , 1974 Davies, 1975;Hu, Loor & Wang, 1975;Mainwaring «fe Jones, 1975; Davies, Thomas & Griffiths, 1976) and post-transcriptional (Ichii, Izawa «fe Murakami, 1974;Liang & Liao, 1975) processes, has emphasized the desirability of a more complete quantitative assessment of ligand reten¬ tion and ligand-receptor interaction. Such an approach might define the imprecise relation¬ ship of cytoplasmic and nuclear receptors (Bruchovsky, Rennie & Vanson, 19756) and clarify the involvement of receptors in synthesis of macromolecules (Davies et al 1976).…”