Effects of antipyrine on umbilical and regional metabolism in late gestation in the fetal lamb.

Abstract

Antipyrine has been used extensively in fetal metabolic studies and is now known to inhibit prostaglandin synthesis; therefore we wished to determine the effects of antipyrine on fetal umbilical and regional metabolism. Chronically catheterized fetal lambs were randomly assigned to antipyrine (n = 6) or control (n = 5) groups. Animals in the antipyrine group were infused with antipyrine (mean +/- SD 9.6 +/- 0.9 mg/min for 165 +/- 38 minutes), and control group animals were not infused. Measurements were made of fetal blood gases, oxygen content, glucose, lactate, lower-body blood flow, upper-body flow distribution, and substrate uptakes across the umbilical and hind limb circulations. The unpaired t test, correlation coefficient, and regression analysis were used for comparisons. There were no differences in antipyrine and control group animals with respect to blood gases, metabolite levels, umbilical blood flow, or umbilical uptakes. Hind limb blood flow (p < 0.10) and oxygen uptake (p < 0.05) were lower and lactate production was higher (p < 0.01) in antipyrine animals than in control group animals. Duration of antipyrine exposure correlated directly with hind limb lactate production (r = 0.85, p < 0.001) and inversely with hind limb oxygen uptake (r = -0.65, p < 0.05). The distribution of blood flow within the fetal upper body also differed between groups, with higher cardiac distribution in the antipyrine group (p < 0.025). Antipyrine does not affect umbilical metabolism but does affect carcass metabolism and fetal blood flow distribution.