Enhancement of hydroxyindole-O-methyltransferase and DNA-dependent RNA polymerase activities induced by oestradiol in rat pineals in culture.
1. Hydroxyindole-O-methyltransferase and DNA-dependent RNA polymerase activities were determined in the pineal gland removed from the ovariectomised rat and cultured under various experimental conditions. 2. The transferase activity declined very slowly during 24 h of incubation. 17beta-Oestradiol significantly increased the transferase activity within 2h after the addition, and the extent of increase was dose-dependent within the concentration range from 0.1 to 15 nM, being increased by 80% at 15 nM. Enhancement of the transferase activity by oestradiol was abolished not only by inhibitors of protein synthesis (cycloheximide and puromycin), but also by those of RNA synthesis (actinomycin D and alpha-amanitin). It was also blocked by clomiphene citrate, an agent which is known to inhibit the binding of steroid hormones to their respective receptors. 3. RNA polymerase activity (forms A and B) declined rapidly during the initial period of pineal culture. Oestradiol (15 nM) increased the RNA polymerase B activity by 50% within 2 h after the addition. The increase was dose-dependent within the concentration range from 0.1 to 15 nM, and was abolished by clomiphene citrate. 4. The possibility is suggested that the pineal is a target organ of oestradiol, and that the steroid-induced reaction sequence in the pineal conforms to that is known in other target organs.
D000121:Acetylserotonin O-Methyltransferase / Q000096:biosynthesis*; D000546:Amanitins / Q000494:pharmacology; D000818:Animals; D002369:Castration; D002996:Clomiphene / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D012321:DNA-Directed RNA Polymerases / Q000096:biosynthesis*; D003609:Dactinomycin / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D007700:Kinetics; D008780:Methyltransferases / Q000096:biosynthesis*; D009924:Organ Culture Techniques; D010870:Pineal Gland / Q000187:drug effects / Q000201:enzymology*; D011691:Puromycin / Q000494:pharmacology; D051381:Rats
D000546:Amanitins; D003609:Dactinomycin; D002996:Clomiphene; D011691:Puromycin; D004958:Estradiol; D003513:Cycloheximide; D008780:Methyltransferases; D000121:Acetylserotonin O-Methyltransferase; D012321:DNA-Directed RNA Polymerases