In vivo effect of androgen and cycloheximide on the RNA synthesis in isolated nuclei of rat ventral prostates.

Castration results in a rapid decrease in the activity of RNA polymerase I (or A) of isolated nuclei of rat prostates. The decrease was mainly ascribed to the diminution in the number of in vivo initiated RNA chains. The "free form" activity of the enzyme, however, which was estimated by the use of exogenous template and actinomycin D, increased 24 h after castration, then dropped rapidly. The administration of testosterone to castrated rats caused an increase in the activities of both RNA polymerases I and II (or B), which started 2 h and reached the maximum 12 h after the administration. No initial rise in RNA polymerase II activity was observed during the first 2 h. The administration of cycloheximide to normal rats caused a very rapid decrease of the activity of template-bound RNA polymerase I of isolated prostatic nuclei (t1/2=1.7 h), while the "free form" activity of the enzyme did not appreciably change until 3 h. The androgen-stimulated increase in the "engaged form" of the RNA polymerase I of isolated nuclei was completely abolished by the administration of cyclohexmide 60 min before killing. Based on the results obtained, the role of protein(s) with a rapid turn-over which is/are androgen-dependent and presumably participating in the control of preibosomal RNA synthesis is discussed.