Melatonin concentration in plasma, pineal gland and duodenum of pregnant rats and their fetuses after melatonin and phenytoin administration

Melatonin (MEL) is involved in regulation of variety of physiological processes. Beside the pineal gland, the presence of MEL was confirmed in the gastrointestinal tract (GIT), where it may exert multiple actions. We investigated the effects of a single MEL administration of 0.4, 4.0 and 40.0 mu g MEL/ml of tap water on MEL levels in rat plasma, pineal gland and duodenum. In addition, we studied the effect of a prolonged administration of MEL, an anticonvulsant drug phenytoin (PHT) and a combination of MEL + PHT, on MEL concentrations in pregnant rats and their fetuses. Single MEL administration of 4.0 and 40.0 mu g MEL/ml resulted in a dose-related increase of MEL concentration in the rat plasma and duodenum but in a decrease of MEL in the pineal gland. After a prolonged MEL administration, MEL levels in duodenal tissues were significantly lower in control group and group treated with PHT as compared to animals, where MEL and PHT were administered simultaneously. A significant increase in MEL concentration was recorded in the intestine of fetuses taken from mothers treated with MEL and MEL + PHT. Our results indicate a dose-related absorption of MEL from tap water to GIT tissues of pregnant rats and their fetuses, where MEL may increase the protection of the intestinal mucose.