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Formation and retention of cotinine during placental transfer of nicotine in human placental cotyledon.

Abstract：

:Maternal smoking during pregnancy causes reduction of fetal breathing movements, an effect attributed to nicotine in fetal blood. Nicotine is metabolized to cotinine which has a long plasma half-life and exhibits slow clearance across membrane barriers. It is also known to activate placental phospholipase-A2-like enzymes, resulting in formation of prostaglandins. Therefore, we studied transport of nicotine in isolated perfused cotyledon of normal human term placenta. The placental cotyledon was perfused with aerated (21% O2, 5% CO2) Krebs-Ringer bicarbonate buffer (pH 7.4, 37 degrees C) containing 2% albumin on both maternal (230 ml, 15 ml/min, 35 mm Hg) and fetal (93 ml, 1.75 ml/min, 70 mm Hg) sides in a closed recirculating system. Nicotine (2 mg) was added to the maternal perfusate; perfusate samples (1 ml) were collected from both sides at regular intervals and analyzed for nicotine and cotinine by high-pressure liquid chromatography. This study gave the following results: (1) In about 60-80 min, 18.6% of the nicotine added to the maternal perfusate was transferred to the fetal perfusate, and the maternal/fetal concentration ratio reached 1.0. These results show rapid placental transfer of nicotine, consistent with its high lipid solubility. (2) Less than 1% is metabolized to cotinine in placenta. The ratio of cotinine concentrations in maternal and fetal perfusates reached 1.0 in about 40 min. These studies were also verified using 14C-nicotine. (3) Maximal reduction in fetal breathing movements occurs at about 30 min, and recovery occurs at 90 min after tobacco smoking by the mother. These observations agree with the rate of placental transfer of nicotine. (4) When nicotine was added on the fetal side, part of it was metabolized to cotinine. However, the maximal concentration of cotinine was twice higher on fetal than on maternal side. These observations suggest that accumulation of cotinine on fetal side may activate prostaglandin formation and trigger spontaneous abortions in pregnant smokers.

journal_name

Pharmacology

journal_title

Pharmacology

authors

Sastry BV,Chance MB,Hemontolor ME,Goddijn-Wessel TA

doi

10.1159/000028231

subject

Has Abstract

pub_date

1998-08-01 00:00:00

pages

104-16

issue

eissn

0031-7012

issn

1423-0313

pii

pha57104

journal_volume

pub_type

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Formation and retention of cotinine during placental transfer of nicotine in human placental cotyledon.