Regulation of Nucleic Acids of Muscles and Accessory Sex Organs of Guinea Pigs by Androgens1

Abstract

Male guinea pigs were castrated at approximately 550 g body weight and androgens were administered by subcutaneous implantation of pellets (approximately 15 mg each) for intervals up to 35 days in 2 series of experiments beginning at 21 and 220 days after castration. The weight, RNA and DNA of the oblique and the gastrocnemius muscles were not changed by either castration or androgen administration. The older animals had heavier muscles with a proportionate increase in RNA but no change in total DNA. The RNA of representative androgenresponsive muscles—temporal and masseter— was lower in the castrated animals. Testosterone produced an immediate maximum increase within 5 days in RNA, which was maintained but was not increased further by continued androgen administration. Castration retarded the attainment of the adult level of the DNA in the temporal and the masseter muscles. Prolongation of castration was accompanied by a very gradual increase in the DNA of these muscles, with an attainment of the normal level within 230 days. The administration of testosterone for 35 days produced no detectable response in the DNA of either the young or old animals. The nucleic acids of the seminal vesicles and prostate were decreased after castration. The decrease of RNA was greater than of DNA. Testosterone administration restored the weight and the DNA to the adult level and the RNA to above normal within 28 days. (Endocrinology74: 635, 1964)