Reproductive organ DNA and RNA of male and female rats from birth to 100 days of age

Male and female rats were adjusted to six pups per litter and weaned at 20 days of age. Groups of ten males were killed at five‐ to ten‐day intervals between one and 100 days of age and groups of 12 to 45 females were killed between ten and 100 days. Accumulation with age of gonadal, seminal vesicular, and uterine weight, DNA, and RNA, were compared with body growth in relative growth analyses to delimit puberty and quantify reproductive growth. Males and females possessed similar body growth to 40 days, after which age females grew more slowly while males continued rapid growth to 60 days. Relative to body growth, testes grew more rapidly from ten days whereas ovarian growth generally paralleled body growth until 50 days of age. A shift in gonadal RNA/DNA ratio from less than to greater than unity occurred early in puberty in both sexes. Nucleic acid contents of accessory reproductive organs indicated that effective levels of gonadal steroids promote pubertal growth beginning at about 40 days in males and about 33 days of age in females. These marked pubertal growths ended at 70 days in males and 60 days of age in females.