Ontogeny of hepatic peroxisomal uricase activity in the mongrel puppy

Activities of uricase, catalase, and acid phosphatase were measured in the light mitochondrial subcellular fraction of liver from late fetal, neonatal, and adult dogs in order to examine the hypothesis that diminished hepatic peroxisomal uricase activity is responsible for elevated plasma uric acid concentrations in newborn puppies. Late fetal dogs had slightly lower uricase activity than 1-day-old puppies (1.4 +/- 1.0 (S.D.) and 3.9 +/- 0.7 X 10(-5) mumole hydrolyzed/min/g liver, respectively, P less than 0.5), and both were much lower than 30-day-old and adult dogs (46.3 +/- 33.7 and 30.8 +/- 17.6, respectively, P less than 0.50). Comparison with the pattern of development of catalase and acid phosphatase demonstrated nonparallelism with uricase activity lagging behind both other enzymes. Plasma urate concentrations of 0.66 +/- 0.09 (S.D.) mg/dl in fetal animals were higher than the maternal plasma value (0.22 mg/dl), which appears to exclude the possibility that low fetal uricase activity was the result of decreased enzyme substrate.