Melatonin in infants and mothers at delivery and in infants during the first week of life.

To evaluate the possible effect of the extreme and permanent changes in the hormonal milieu and in the lighting conditions at birth on the pineal hormone, melatonin (MT), we measured maternal vein and umbilical artery concentrations of MT in 19 parturients, post-partum urinary concentrations of MT in 14 mothers and their infants, and daytime (0800-2000 h) and night-time (2000-0800 h) urinary concentrations of MT and 6-sulphatoxymelatonin in 22 infants during the first 8 days of life. The mean MT concentrations in maternal venous blood and umbilical arterial blood did not differ significantly from each other and there was a positive correlation between them. The same was true for postpartum urinary MT of the mothers and their infants. There was no diurnal rhythm of MT during the first week of life. MT excretion in neonates was 2-5 pmol/12 h (only 1-5% in comparison with adults) and that of 6-sulphatoxymelatonin 150-300 pmol/12 h. In reverse phase high pressure liquid chromatography (HPLC) studies, 84-100% of total MT immunoreactivity was eluted at the same position as synthetic MT, and a small amount of hydrophobic MT-like immunoreactive material was also detected in five of the 10 urine extracts studied. This material (perhaps a novel neonatal metabolite of MT) may be indicative of immaturity of neonatal metabolism of MT although 6-hydroxylation is also functional in neonates. Although infant MT immediately after delivery at least partly reflects maternal MT secretion, our results show that the pineal gland is capable of producing MT at this time.(ABSTRACT TRUNCATED AT 250 WORDS)