Effects of the uterus and the ovaries on growth, somatotropin and somatomedin A in developing rats.
The effects of hysterectomy and ovariectomy on plasma concentrations of GH, somatomedin A, TSH and thyroxine (T4) were studied in developing rats. Four groups of 24-day-old rats were ovariectomized, ovohysterectomized, hysterectomized or sham-operated. Their weights, lengths and plasma hormone concentrations were measured at 26, 43, 64, 78 and 92 days of age to investigate pre- and postpubertal differences caused by the uterus or ovaries. Plasma concentrations of the hormones examined showed a successive rise with time, but GH and somatomedin A concentrations rose mainly after the opening of the vagina (days 50-55). Higher GH and somatomedin A concentrations were found in the plasma of ovariectomized animals than in ovohysterectomized controls before puberty (GH: 260-300%, P less than 0.01; somatomedin A: 25-30%, P less than 0.05). Ovariectomized animals weighed more than ovohysterectomized females after puberty (4.5-6%, P less than 0.01). This indicated that the uterus exerted a stimulatory effect on GH-somatomedin A regulation and body weight gain in the absence of the ovaries. Significantly lower plasma somatomedin A (but not GH) concentrations were found in hysterectomized and sham-operated animals than in their respective controls after puberty (30-39%, P less than 0.01) and their final body weight was lower (22-26%, P less than 0.001). There were no consecutive uterus- or ovary-related changes in plasma TSH and T4 levels. It was concluded that both the uterus and ovaries had significant as well as opposite effects on somatomedin A and body weight with the effects of the ovaries being greater than those of the uterus.
D000818:Animals; D001835:Body Weight; D005260:Female; D006128:Growth; D013006:Growth Hormone / Q000097:blood*; D007335:Insulin-Like Growth Factor II; D010053:Ovary / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012741:Sexual Maturation; D013002:Somatomedins / Q000097:blood*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014599:Uterus / Q000502:physiology*
D013002:Somatomedins; D007335:Insulin-Like Growth Factor II; D013972:Thyrotropin; D013006:Growth Hormone; D013974:Thyroxine