The transmission of 125I labelled globulins to the circulation in young rats



The total and bound concentration quotients (C.Q.s) developed after intraperitoneal administration of globulin preparations are considerably greater than those developed after oral administration in young rats aged 15, 20, 23 and 27 days.

Over this age range the total C.Q.s developed after intraperitoneal administration decline more sharply than those developed after oral administration, suggesting that the mechanism of protein absorption from the peritoneum becomes comparatively less efficient during this period. At 27 days of age, contrasting with earlier stages, considerable degradation of the intraperitoneally administered dose occurs.

The duodenum of unweaned 28 day old rats is capable of transmitting to the circulation large quantities of labelled globulin with apparently little degradation or selection. This ability is virtually lost by 33 days. The jejunum of unweaned 28 day old rats transmits only very small quantities of labelled globulin to the circulation, and there is considerable degradation of the injected dose.

These several factors are discussed in the general context of the postnatal transfer of passive immunity in this species.