Effects of hypoxia on plasma amino acids and taurine of ovine fetuses

Objective: The purpose of this study was to examine the effects of hypoxia and circulatory insufficiency on taurine and other plasma amino acid levels as adaptive responses of preterm and term gestation ovine fetuses to severe hypoxia in utero.

Methods: During general anaesthesia 13 exteriorized, instrumented ovine fetuses (6 preterm and 7 term gestation) were exposed to sustained hypoxia caused by reduction of uterine blood flow. A vascular occluder placed around the maternal common iliac artery enabled total compression. Transit-time flow probes on both uterine arteries recorded continuously blood flow volume. Before (0%) and during (100%) fetal hypoxia arterial blood samples were taken for biophysical (blood gases, lactate), taurine and fetal plasma amino acids measures. Wilcoxon's test for paired data was used for comparison of values before and during hypoxia.

Results: In contrast to basic values 6 of 20 tested fetal plasma amino acids increased significantly (p < 0.01) during sustained hypoxia, with the largest proportionate changes in taurine. These results were noticed for preterm as well as term gestation ovine fetuses during hypoxia when compared to basic measures and accompanied by elevated lactic acid- and decreased pH- values.

Conclusions: These findings enhance knowledge of fetal adaptive mechanisms to severe hypoxic stress. Taurine and increased fetal plasma amino acids may have been released by the tissues as a protective response against hypoxia-induced inflammation and/or in an attempt to keep osmotic balance. Further studies are needed to determine the influence of taurine and plasma amino acids on fetal development during hypoxia.