Identification of fetuin in human and rat fetuses and in other species

The fetal protein, fetuin, has previously only been identified in species belonging to the order Artiodactyla. Samples of fetal, newborn and adult human (Homo sapiens) and rat (Rattus norvegicus) plasma and tissues have been studied using three techniques: (a) crossed immunoelectrophoresis of plasma against each of four different anti-fetuin antisera (two anti-cattle, one anti-pig and one anti-sheep); (b) the peroxidase-antiperoxidase technique applied to agarose gels containing plasma spots; (c) the indirect immunoperoxidase technique applied to human fetal tissue sections. In human fetal samples all three methods gave evidence for the presence of fetuin except late in gestation and in the newborn. Adult plasma was negative. In rat fetuses only plasma was tested, by methods (a) and (b). Positive reactions were obtained for both fetal and adult samples; the fetal samples cross-reacted with several of the anti-fetuins, adult samples reacted with only one. All the fetal and embryonal plasma samples tested with the peroxidase-antiperoxidase method were positive for fetuin except for the chicken. Thus fetuin appears to be distributed in at least five mammalian orders (Artiodactyla, Primates, Rodentia, Carnivora and Perissodactyla).