Hemopexin synthesis in vitro by human fetal tissues

Serum concentrations of hemopexin, transferrin, and albumin were measured for 12 fetuses between 14 and 36 weeks of gestational age. Hemopexin levels ranged from 7 to 64 mug/ml, transferrin levels ranged from 280 to 928 mug/ml, and albumin levels ranged from 13 to 59 mg/ml. In general, the serum concentrations of these three proteins increased with advancing gestation. Placenta, thymus, and colon did not incorporate 14C-labeled amino acids into hemopexin, transferrin, or albumin. By contrast radioimmune precipitates for five culture supernatants of liver indicated significant synthesis of albumin and hemopexin. [14C]Albumin accounted for 22-73% and [14C]hemopexin 1.1-4.2% of the total 14C-labeled proteins. In each instance, the [14C]transferrin was below 1% of the total 14C-labeled proteins.