Urinary excretion of morphine and biosynthetic precursors in mice

Abstract

It has been firmly established that humans excrete a small but steady amount of the isoquinoline alkaloid morphine in their urine. It is unclear whether it is of dietary or endogenous origin. There is no doubt that a simple isoquinoline alkaloid, tetrahydropapaveroline (THP), is found in human and rodent brain as well as in human urine. This suggests a potential biogenetic relationship between both alkaloids. Unlabeled THP or [1;3; ]-THP was injected intraperitoneally into mice and the urine was analyzed. This potential precursor was extensively metabolized (96%). Among the metabolites found was the phenol-coupled product salutaridine, the known morphine precursor in the opium poppy plant. Synthetic [7D]-salutaridinol, the biosynthetic reduction product of salutaridine, injected intraperitoneally into live animals led to the formation of [7D]-thebaine, which was excreted in urine. [N-CD 3 ]-thebaine was also administered and yielded [N-CD 3 ]-morphine and the congeners [N-CD 3 ]-codeine and [N-CD 3 ]-oripavine in urine. These results show for the first time that live animals have the biosynthetic capability to convert a normal constituent of rodents, THP, to morphine. Morphine and its precursors are normally not found in tissues or organs, presumably due to metabolic breakdown. Hence, only that portion of the isoquinoline alkaloids excreted in urine unmetabolized can be detected. Analysis of urine by high resolution-mass spectrometry proved to be a powerful method for tracking endogenous morphine and its biosynthetic precursors.endogenous morphine | mammalian mophine | morphine biosynthesis | stable-isotope labeled morphine | high resolution-mass spectrometry T he occurrence of endogenous morphine in mammals has been a controversy over the past three decades. Goldstein (1-3) and Spector (4-7) and their associates pioneered the assumption that morphine occurs in mammals and plays an unknown role. Other groups claimed that the morphine found in rodents is of dietary origin (8, 9). Clear answers concerning the presence of morphine in animals have been obscured by inadequate experimentation and possible laboratory contamination with morphine. Only recently, several reports appeared using sterile human cell cultures and isolated organs, which added to a body of evidence that morphine indeed occurs in mammals and human cell cultures (10-12). To substantiate these findings, we made use of the fact that morphine is excreted in urine of humans (13-15) and rats (7). The presence of morphine in urine has been unequivocally demonstrated by mass spectrometry (15), but the origin of the excreted morphine has not yet been clarified. If these trace amounts of morphine in urine are formed de novo (and are not from dietary intake), a biosynthetic apparatus should be present in mammals that catalyzes this multistep pathway.The goal of this investigation is to demonstrate the de novo formation of benzylisoquinoline alkaloids, mainly of the morphinan type, in live rodents. Our experimental strategy involves administration of stable-...

Mu Opioids and Their Receptors: Evolution of a Concept

“…First proposed by Gintzler and Spector using immunologic techniques (Gintzler et al, 1978;Shorr et al, 1978;Donnerer et al, 1986Donnerer et al, , 1987Grobe et al, 2010), these observations are supported by several other laboratories (Hazum et al, 1981b;Killian et al, 1981;Goldstein et al, 1985;Weitz et al, 1986). The question arose whether the endogenous morphine is synthesized in the brain or whether it is absorbed from foodstuffs, particularly with its isolation from milk and plants other than the poppy (Hazum et al, 1981b).…”

“…The question arose whether the endogenous morphine is synthesized in the brain or whether it is absorbed from foodstuffs, particularly with its isolation from milk and plants other than the poppy (Hazum et al, 1981b). Although ingestion remains one potential mechanism for accumulation of endogenous morphine, there is evidence it can be synthesized de novo by mammals (Goldstein et al, 1985;Weitz et al, 1987;Poeaknapo et al, 2004;Boettcher et al, 2005;Grobe et al, 2010) and even in isolated cells (Poeaknapo et al, 2004;Boettcher et al, 2005;Han et al, 2010). In addition to morphine, other metabolites have been isolated from brain, including morphine-6b-glucuronide and morphine-6-sulfate (Fig.…”

Cytochrome P450 3A Enzymes Catalyze the O6-Demethylation of Thebaine, a Key Step in Endogenous Mammalian Morphine Biosynthesis

“…9). Administration of (R,S)-tetrahydropapaveroline to mice yielded reticuline, salutaridinol, thebaine, and oripavine in urine (24). All of the oxidation steps following the formation of tetrahydropapaveroline have now been characterized in humans in vitro.…”

“…1) (21). Both of these pathways are plausible, in that thebaine, codeine, and oripavine are present in both mammals as well as the opium poppy (5,(22)(23)(24).…”

Recent Advances in the Chemistry of Oripavine and Its Derivatives

“…The biosynthesis of endogenous morphine was observed when tetrahydropapaveroline was injected intraperitoneally into mice and the urine was analyzed [26]. The biosynthesis of morphine proceeds via (R)-reticuline to salutaridine, salutaridinol and thebaine, all of which were found in mice urine after injection of relevant precursors.…”