Abstract
Pregnant primates have been shown to have a large diurnal (24-hr) rhythm in circulating melatonin (MEL). We examined whether alterations in circulating maternal MEL could be transferred to the fetus by giving i.v. injections or infusions of MEL to pregnant monkeys. Three rhesus monkeys with timed gestations (± 1 d) underwent hysterotomy at 151 d gestation. [3H]MEL levels were determined by chloroform-extraction and authenticated by TLC in the injection studies; MEL plasma levels were measured by RIA in the infusion studies.
Three min after a maternal injection of a trace amount of [3H]MEL (lμg, 150μCi) fetal plasma [3H]MEL levels were 84 ± 9% (SE) of maternal [3H]MEL levels (168 ± 14 pg/ml). Parallel rates of disappearance occurred in both circulations over 30 min. Peak amniotic fluid [3H]MEL levels of 17 ± 2% maternal plasma levels occurred at 30 min. Postmortem examination of CSF from 2 fetuses showed [3H]MEL levels equal to fetal plasma levels.
To mimic endogenous changes in maternal MEL, 0.4 μg/min authentic MEL was infused to the mothers for 20 min. Prompt 6- to 12-fold MEL increments occurred in both circulations; parallel decrements occurred following the infusion.
These findings indicate the MEL, the putative pineal hormone, is rapidly transferred to the fetus in late primate pregnancy. The placental transfer of MEL may introduce the fetus to 24 hr periodicity and provide information about ambient lighting.
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Reppert, S., Chez, R. & Klein, D. 331 MATERNAL-FETAL TRANSFER OF MELATONIN IN THE NONHUMAN PRIMATE. Pediatr Res 12 (Suppl 4), 419 (1978). https://doi.org/10.1203/00006450-197804001-00336
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DOI: https://doi.org/10.1203/00006450-197804001-00336