Uroprotein excretion in neonates and infants.

In 5 neonates and 5 infants urinary proteins were investigated for quantity, molecular weight and fibrinolytic activity, the urine of 5 adults serving as a control. The uroproteins were concentrated and fractionated by means of molecular sieving (Sephadex G-150). Urokinase activities were determined on native human fibrin plates. 1. The distribution of the uroproteins among the various molecular classes showed no difference between age groups. 2. In all age groups urokinase activities were present in the ranges of molecular weights 30000, 60000 and above 100000, representing the monomer, dimer and polymer forms of urokinase. 3. There is a significant difference between the distribution of the urokinase activities over the molecular weight ranges in the different age groups. In neonates 70% of the urokinase is present as monomer, 25% as dimer and 5% as polymer, while in infants and adults the urokinase is present in about equal parts as mono-, di-and polymer.