t-PA activity and antigen in the newborn and infant

Concentrations of tissue plasminogen activator (t-PA) activity and t-PA antigen in blood obtained from neonates were investigated in order to elucidate a fibrinolytic condition of the neonates and compare with that of the infants and children. The t-PA activity was measured by bioimmunoassay using monoclonal antibody (SP-322), which bound with an epitope nonintervening with active site of t-PA. The t-PA antigen was detected by ELISA using the same monoclonal antibody (SP-322). As a result, t-PA activity in blood from the newborn baby increased to 0.97 +/- 0.48 IU/ml at the second to the fifth day, and decreased gradually to the baseline levels of healthy adult until 15 years old. The t-PA antigen level was increased from the seventh day. These results suggests that t-PA activity in blood from the neonates may be higher concentrations than those from the infants, children and adults.