Abstract
Summary
1. Eighteen 24-hour urine samples collected from one woman during nulligravid, gravid and lactating periods, were analyzed for the free indispensable amino acids—leucine, isoleucine, valine, histidine, lysine, methionine, phenylalanine, arginine, threonine and tryptophan. The excretion level for each amino acid increased from the nulligravid to the gravid state, evident as early as the second month of gestation. Excretion of threonine continued to increase during gestation while methionine fluctuated slightly from the non-pregnant value. The other 8 amino acids showed a decreased excretory level during the fourth and fifth months of gestation. From the sixth to the ninth months, excretion levels of most of the amino acids increased slightly or remained fairly constant. 2. During lactation, the excretion level for each amino acid is less than that for pregnancy or non-pregnancy. 3. Threonine, histidine, lysine and tryptophan showed the greatest changes from one phase of the reproductive cycle to another. 4. While trends of amino acid excretion were similar from one pregnancy to another, the quantities excreted in relation to duration of gestation were different.
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