TESTICULAR CHROMATIN ACTIVATION IN HYPOPHYSECTOMIZED RATS

Incorporation of labeled thymidine into testicular DNA of hypophysectomized rats began to increase after the administration of testosterone propionate [TP] and chorionic gonadotropin [CGn]. While the thymidine incorporation reached maximum in 4 days, the DNA polymerase activity did not culminate until 8 days after the initiation of hormone treatment. The high molecular weight (6-8 S), presumably cytoplasmic DNA polymerase accounted almost entirely for this increase. Administration of TP and CGn to hypophysectomized rats increased testicular RNA polymerase and chromatin templating activity. Chain elongation and initiation studies revealed that the increased templating capacity of androgen-stimulated testicular chromatin was almost entirely caused by the increase in the number of initiation sites. While the nuclear polymerase I responded relatively rapidly to hormone stimulation and reached a prominent maximum in about 3 days, the activity of polymerase II was more sluggish and not as prominent. The in vivo incorporation of ortho[32P]phosphate into chromosomal phosphoproteins occurred early during the androgen treatment and reached a maximum in about 20 h. The protein phosphokinase activity peaked later, approximately 72 h after the first administration of hormones.