Mass spectrometric identification and quantification of endogenous 5-methoxyindole-3-acetic acid in quail tissues

The endogenous levels of 5-methoxyindole-3-acetic acid (5-MIAA) in quail pineal gland, retina and serum were determined by capillary column gas chromatography/mass spectrometry/selected ion monitoring using a deuterated internal standard and the N-pentafluoropropionyl-O-pentafluorobenzyl ester derivative. Diurnal rhythms of pineal and serum 5-MIAA with high levels at mid-light and low levels at mid-dark suggest a pineal origin of 5-MIAA in the blood. In contrast, retina displayed an opposite diurnal rhythm of 5-MIAA with high levels at night, suggesting that the biosyntheses of 5-MIAA in the quail pineal gland and retina were different. In vitro studies on incubation media indicated that both the pineal gland and retina are capable of synthesis/secretion of 5-MIAA.