Serum alpha-fetoprotein, albumin, and gamma-G-globulin in the human conceptus.

Abstract

Serum concentrations of alpha fetoprotein (AFP) in the human conceptus were investigated and compared to the concentrations of albumin and gamma G-globulin. Determinations were made immunochemically over gestational periods from 6.6-39 weeks and in the 1st 3 weeks of newborn life. Serum concentation of AFP increased from 6.6 weeks reaching maximal at about 13 weeks at which time the level decreased rapidly to levels less than 2% of maximum by 34 weeks. Newborn at term had detectable AFP but that disappeared from serum with an average half-life of 5 days during the 1st week of life and with an average half-life of 3 days after the 1st week. Serum albumin levels reached a plateau by 22-24 weeks of gestation remaining at these levels throughout the neonatal period. Average concentrations of albumin in neonatancy were slightly higher than those in mothers. Gamma G-globulin serum concentrations from 6.6-22 weeks of gestation were less than .2 gm/100 ml. After 22 weeks gamma G-globulin increased to levels seen in term infants by 26 weeks. Albumin:AFP ratios in amniotic fluid were much higher than those in bladder urine from 11-13.2 weeks of gestation which indicates the possible existence of an additional source of amniotic fluid albumin besides urine. Clearance of albumin into urine was greater than that of AFP. By gel filtration and ultracentrifugation the molecular size of AFP was similar to that of albumin. Sera of pregnant women did not contain detectable amounts of AFP.