Effects of hypoxia on plasma amino acids of fetal sheep

Secondary amino acid disturbances from circulatory responses during hypoxia may cause problems in interpreting plasma amino acid profiles of sick babi es investigated for possible inherited defects. Systematic studies to chara cterise them are difficult in man. We investigated the effects of hypoxia o n plasma amino acids by studying 9 late gestation fetal sheep in utero duri ng 11 one hour episodes of moderately severe isocapnic hypoxia. In 6 experi ments, maternal plasma amino acids were also monitored. Fourteen fetal plas ma amino acids increased significantly, with the largest proportionate chan ges in alanine, valine, leucine, isoleucine, phenylalanine, tyrosine, ornit hine and lysine. Maternal amino acids did not increase. Probable explanatio ns were reflex peripheral vasoconstriction in skeletal muscle beds and decr eased hepatic blood flow. The findings extend our knowledge of the fetal re sponse to hypoxic stress, demonstrate the importance of skeletal muscle in branched-chain amino acid metabolism, and should help with interpretation o f postnatal plasma amino acid disturbances.