A number of tremorogenic β-carboline alkaloids have been found in common plant-derived foodstuffs, beverages, and inhaled substances. Because of their natural presence in the food chain, there is a growing concern regarding the potential risks of certain essen tial tremors associated with the long-term low-level dietary exposure to these alkaloids. The purpose of this study was to develop an effective analytical method to determine blood levels of two major β-car boline derivatives, harmane and harmine. Human blood was extracted with ethyl acetate and methyl-tbutyl ether (2:98) under an alkaline condition. After evaporation of organic solvent, the samples were re-constructed in methanol. The samples were fraction ated on a 250 × 4.6-mm C18 reversed-phase column with an isocratic mobile system consisting of 17.5 mM potassium phosphate buffer (ph 6.5) and methanol (30: 70), followed by an on-line fluorescence detection. The method had the detection limit to determine 206 and 81 pg/ml of harmane and harmine, respectively, in 10 ml of human blood. The intraday precision (C.V.) at 25 ng/ml was less than 6.7 and 3.4% for harmane and harmine, respectively. The interday precision was 7.3% for harmane and 5.4% for harmine. The method has proven sensitive, reproducible, and thus useful for both laboratory and clinical studies of β-carboline toxicities.A number of tremorogenic β-carboline alkaloids such as harmane, harmine, harmaline, and ibogaine have been found in common plant-derived foodstuffs (wheat, rice, corn, barley, soybeans, rye, grapes, mushrooms, vinegar). plant -derived beverages (wine. beer. whisky. brandy, sake). and plant-derived inhaled substances (tobacco) (1, 6). These substances are also endogenous to animal tissue (6, 9) and have been isolated in beef and sardines (1). Laboratory animals exposed to these chemicals result in an acute action tremor (5). Because of their natural presence in the food chain, it is conceivable that the route of exposure in humans would be from dietary sources, smoking. and consumption of alcoholic beverages. In fact, the occurrence of β-carbo-lines in human blood under normal physiological Copyright © 2000 by Academic Press All rights of reproduction in any form reserved. Rommelspacher et al. employed thin-layer gel-plate separation and mul tiple extraction followed by high-performance liquid chromatography (HPLC) to detect 6-0H-tetrahydronorharmane (6-0H-THN) in rat and human sam ples (9). The substantial precolumn preparation in that study limited its application to clinical monitoring of this and other β-carbolines. Moncrieff also reported an HPLC method for tissue harmane, harmine, and harmaline (4). However, the quantitation of three compounds required three different mobile phases and three separate HPLC runs. A better HPLC method was developed by Adachi et al.(1) for determination norharmane and harmane in foodstuffs. Nevertheless, the adaptability of this method to biological remains uncertain. Moreover, to the best of our knowledge, there has been no report ...

Immortalized rat choroidal epithelial Z310 cells have the potential to become an in vitro model for studying transport of materials at blood-cerebrospinal fluid barrier (BCB) (Shi and Zheng, Brain Research 1057:37-48, 2005). This study was designed to demonstrate the presence of tight junction properties in Z310 cells and the functionality of Z310 monolayer in transport of selected model compounds. Western blot analyses revealed the presence of claudin-1, ZO-1, and occludin in Z310 cells. Transmission electron microscopy showed a "tight junction" type of structure in the sub-apical lateral membranes between adjacent Z310 cells. Real-time RT-PCR revealed that Z310 cells expressed representative transporters such as DMT1, MTP1, TfR, p-glycoprotein, ATP7A, ZnT1, ABCC1, Oat3, OCT1 and OB-Ra. Moreover, Z310 cells cultured in a two-chamber Transwell device possessed the ability to transport zidovudine (anionic drug), thyroxine (hormone), thymidine (nucleoside), and leptin (large polypeptide) with kinetic properties similar to those obtained from the in vitro model based on primary culture of choroidal epithelial cells. Taken together, these data indicate that the Z310 BCB model expresses major tight junction proteins and forms a tight barrier in vitro. The model also exhibits the ability to transport substances of various categories across the barrier.

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