Thromboxane B2 production by fetal and neonatal platelets: effect of idiopathic respiratory distress syndrome and birth asphyxia.

To study the production of proaggregatory thromboxane A2 (TxA2) by fetal and neonatal platelets, blood specimens were collected from umbilical cords immediately after delivery at term (n = 22), from newborn infants during the first 10 days of life (n = 85), from infants between 1 and 3 months of age (n = 14), and from healthy adults (n = 18). The blood samples were allowed to clot spontaneously at +37 degrees C for 60 min, and the concentrations of thromboxane B2 (TxB2), a stable metabolite of TxA2, in the sera were measured by radioimmunoassay and expressed as nanograms of TxB2/10(6) platelets. Platelet TxB2 generation in term infants at the age of 1 day (1.344 +/- 0.253 ng/10(6) platelets, mean +/- SE, n = 9) was higher than that in cord blood (0.634 +/- 0.042 ng/10(6) platelets, n = 22), or in infants of 1-3 months of age (0.881 +/- 0.099 ng/10(6) platelets, n = 14), or in adults (0.869 +/- 0.062 ng/10(6) platelets, n = 18). Increase in TxB2 generation following birth was seen already at the age of 1 h (1.076 +/- 0.114 ng/10(6) platelets, n = 9). TxB2 synthesis in preterm infants (1.032 +/- 0.136 ng/10(6) platelets, n = 10) did not differ from that in term infants on the 1st day of life, and idiopathic respiratory distress syndrome had no effect on it (1.029 +/- 0.079 ng/10(6) platelets, n = 19). Severe birth asphyxia was accompanied by reduced TxB2 formation (0.564 +/- 0.201 ng/10(6) platelets, n = 7).(ABSTRACT TRUNCATED AT 250 WORDS)