Plasma immunoreactive-trypsin(ogen) levels during development.

We previously showed that the uptake of intact trypsin from the intestine of suckling animals was greater than that of weaned animals. To extend these studies, we measured plasma cationic immunoreactive-trypsin(ogen) in human subjects aged 3 days to 43 years. In agreement with the observation of other investigators, we found that the concentration of cationic immunoreactive-trypsin(ogen) was significantly increased in 3-day-old infants compared with other age groups. None of the cationic immunoreactive-trypsin in adult samples was bound to alpha 1-antitrypsin, whereas 28% of cationic immunoreactive-trypsin in infant samples was bound to alpha 1-anti-trypsin.