thromboxane-a2 and Jaundice--Neonatal

To study the effects of hyperbilirubinemia on platelet thromboxane A2 (TxA2) and vascular prostacyclin (PGI2) production in newborn infants, the stable metabolites of these prostanoids, thromboxane B2 (TxB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), respectively, were studied in 48 hyperbilirubinemic (serum total bilirubin concentrations between 100 and 320 mumol/1) term infants before and after phototherapy at the age of 2-10 days. The effect of bilirubin on platelet TxA2 production was also determined in vitro. The production of TxB2 during spontaneous clotting in infants with moderate hyperbilirubinemia (serum total bilirubin 171-250 mumol/1) was higher than that in infants with mild (serum bilirubin 100-170 mumol/1) or marked (serum bilirubin greater than 250 mumol/1) jaundice. There was, in addition, an inverse correlation (r = -0.625, p less than 0.01, n = 20) between TxB2 formation and serum total bilirubin concentrations in infants with total bilirubin concentrations over 170 mumol/1. Platelet TxB2 production was enhanced at low (200 mumol/1), but decreased at high (400-1600 mumol/1) concentrations of bilirubin in vitro. Although phototherapy reduced the serum bilirubin levels, it did not change the TxB2 generation. Neither hyperbilirubinemia nor phototherapy had any effect on the plasma 6-keto-PGF1 alpha levels. The results indicate a dual effect of bilirubin on the TxA2 production in neonatal platelets. This may contribute to the hemostatic disturbances in neonatal hyperbilirubinemia.

Topics: 6-Ketoprostaglandin F1 alpha; Blood Platelets; Humans; Infant, Newborn; Jaundice, Neonatal; Phototherapy; Thromboxane A2; Thromboxane B2; Thromboxanes