Plasmaβ-Endorphin,β-Lipotropin, and Met-Enkephalin Concentrations during Pregnancy in Normal and Drug-Addicted Women and Their Newborn

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Abstract
Most studies of plasma β-endorphin concentrations in pregnant women show that these are highly elevated. This might indicate a role for opiate peptides during pregnancy and in the fetus-mother relationship. We measured plasma β-endorphin, β-lipotropin, and met-enkephalin concentrations in normal and drug-addicted women during pregnancy, labor, and delivery, and in their newborn infants. Peptides were measured by RIA after extraction and concentration on silica columns and separation by high pressure liquid chromatography. In both normal and drug-addicted mothers we found an increase in plasma β-endorphin during pregnancy, without a concomitant increase in plasma β-lipotropin or met-enkephalin. Only β-lipotropin increased dramatically in both groups at delivery, whereas β-endorphin and met-enkephalin remained unchanged. Peptide concentrations in umbilical plasma were similar to those in peripheral plasma of the mothers. On day 1 of life plasma β-endorphin, β-lipotropin, and met-enkephalin concentrations in the newborn from normal mothers were higher than in nonpregnant adult subjects and gradually decreased toward normal adult values by day 5 of life. Plasma β-endorphin, β-lipotropin, and met-enkephalin concentrations of newborn infants of drug-addicted mothers increased dramatically on day 2 and 3 of life, up to 1000-fold the concentrations of normal adults, and remained elevated up to 40 days after birth. In conclusion, β-endorphin, β-lipotropin, and met-enkephalin concentrations during pregnancy are not affected by drug addiction, whereas in the newborn of drug addicted mothers concentrations of these compounds are markedly increased.