Effect of decapitation and ACTH on somatic development of the rabbit fetus

Rabbit fetuses were decapitated, injected with ACTH or decapitated and injected with ACTH on day 24 of gestation. On day 29 the body weight and weight of the interscapular fat pad were compared with those of littermates. The weight, total DNA and weight/DNA ratio of the liver, heart and kidney were measured in experimental and control fetuses. A comparison was made between decapitated and control fetuses of the length of the hind limb bones and number of ossified vertebrae. The body weight of the decapitated or ACTH-injected fetus ranked significantly below the mean for the litter, but decapitated fetuses injected with ACTH ranked close to the litter mean. The growth retardation of the decapitated fetus was not manifest in the kidneys which were heavier and had a greater number of cells than normal, nor in the cell size of the heart, liver or kidneys which were equal to those of the heaviest fetus in the litter. Decapitation had no specific effect on ossification. Growth retardation of the ACTH-injected fetus was mirrored by different patterns of DNA and weight/DNA reduction in the three organs studied. Decapitation retards growth in body weight of the fetal rabbit which may be corrected by ACTH. It is concluded that the hypophyseal-adrenal axis plays a role in the control of normal fetal growth but that excess secretion of glucocorticoids results in stunting.