The absorption of 131I-labelled homologous and heterologous serum proteins fed orally to young rats

Abstract

Three hours after feeding with homologous I131-labeled whole adult rat serum, the blood of suckling rats 7- and 14-days old contained significant amounts of labeled globulins, amounting to about 7.5% of the globulins contained in the dose serum. When bleeding was deferred until 24 hours after feeding, about 2.4% of the globulins in the dose serum could be detected in the blood. This lower figure was probably due to the equilibration of the absorbed globulins between the plasma and the extravascular pool. Rats which were 21 days old at the time of feeding (an age when they are normally weaned) absorbed less than 0.5% of the globulins contained in the dose serum. In rats of all ages very little labeled albumin (0.2%) could be detected in the blood 3 and 24 hours after feeding. Similarly, 7- and 14-day-old rats when fed with labeled whole adult rabbit or monkey serum, absorbed significant but smaller amounts of globulin and very little albumin.