Abstract
Levels of α2-plasmin inhibitor (α2 PI) activity and antigen were measured in normal infants and children from 1 month to 15 years of age. In 100 normal adults, the mean values of α2 PI activity were 102.2±11.9% in a fibrinolytic method improved by author, 104.9±11.9% in an amidolytic method devised by author and 103.7±12.4% in Matsuda's amidolytic method. The levels of α2PI antigen was 103.0±12.3%. In 50 infants at 1 month of age, the mean values of α2 PI activity were 109.5±14.8% in the fibrinolytic method, 107.6±14.3% in the author's method and 110.2±12.8% in Matsuda's method. The levels of α2 PI antigen was 109.4±13.9%. These values were increased with age and reached peak at 6-9 months and then decreased gradually with increasing age. The values of 11-15 years group reached almost the same values as that of adult group. There was no significant difference in α2 PI activity and α2 PI antigen or between male and female in each age group. This chronological change of α2 PI was similer to that of α2-globulin and that of α2-macroglobubin.
The increase of both α2 PI activity and antigen in the latter half of infancy period suggests the increased synthesis in the liver, but the essential cause is unknown.
