Abstract
The profile of appearance and disappearance of α-fetoprotein (AFP) in the serum of analbuminemic rats, which have a genetically controlled lack of serum albumin, was studied. During the perinatal stage, AFP was present in the serum of analbuminemic rats, its concentration at birth being 10 mg/ml as in normal rats. In analbuminemic rats, the concentration of serum AFP remained at about 10 mg/ml during the first week after birth and then decreased rapidly during the next 2 weeks, becoming undetectable about 4 weeks after birth. In normal rats, the serum AFP concentration reached a maximum of 11.5 mg/ml at birth and then decreased sharply to an undetectable level within 4 weeks after birth, although a small rebound of AFP concentration was observed about 1 week after birth. AFP synthesis in analbuminemic and normal rats was examined by injecting [3H]leucine i.p. and then measuring the radioactivity incorporated into the acid-insoluble fraction and immunoprecipitable fraction using anti-AFP antiserum. In analbuminemic rats, synthesis of AFP amounted to 7.5% of the total protein synthesis at birth and was maintained at about 7% of the total for the first week after birth and then decreased to 2% at 2 weeks after birth. In normal rats, AFP synthesis also amounted to 7.5% of the total protein synthesis at birth but decreased to about 2% at 2 days after birth and then remained at a low level for about 2 weeks. In both normal and analbuminemic rats, AFP synthesis was undetectable at 4 weeks after birth. These data show that AFP synthesis is shutoff after birth irrespective of the serum albumin concentration during neonatal development.
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