Correlation of plasma hypoxanthine and catecholamine levels in the umbilical vein

Hypoxanthine and the catecholamines, dopamine, norepinephrine and epinephrine were determined in umbilical venous cord plasma in 27 term babies delivered vaginally. When correlating hypoxanthine with log epinephrine a weak positive linear correlation was found (r = 0.45, p less than 0.05). The correlation between hypoxanthine and log dopamine showed a significant negative linear correlation (r = -0.65, p less than 0.01). There was also a significant correlation between log epinephrine and pH (r = 0.72, P less than 0.01) and base deficit (r = 0.46, P less than 0.05). In four babies who suffered intrauterine hypoxia, hypoxanthine was significantly elevated compared with non hypoxic babies (21.4 +/- 5.1 versus 6.3 +/- 6.6 mumol/l, P less than 0.01). In these babies norepinephrine (3710 +/- 3888 vs 789 +/- 718 Pg/ml, P less than 0.01) and epinephrine (298 +/- 229 vs 148 +/- 116 Pg/ml, P less than 0.05) were significantly elevated as well, in contrast to dopamine levels (188 +/- 94 vs 169 +/- 134 Pg/ml N. S.). This finding seems to indicate that dopamine synthesis goes down during hypoxia probably because the rate limiting enzyme in dopamine synthesis, tyrosine, hydroxylase, is inhibited in hypoxia.