Urinary excretion of 4-hydroxyamphetamine and amphetamine in male and female Sprague-Dawley and Dark Agouti rats following multiple doses of amphetamine

Differences in cytochrome P450 and nuclear receptor mRNA levels in liver and small intestines between SD and DA rats

This study aimed to clarify the differences in mRNA levels of cytochrome P450 (CYP) isoforms and nuclear receptors between Dark Agouti (DA) and Sprague-Dawley (SD) rats which are animal models for poor metabolizers and extensive metabolizers for CYP2D6, respectively. Using liver and small intestine tissues of both rat strains, we investigated the mRNA levels of CYP1A, 2A, 2B, 2C, 2D, 2E, and 3A subfamilies and nuclear receptors which regulate the transcription of CYP isoforms. In the liver, male DA rats showed a low CYP2D2 mRNA level but high mRNA levels of CYP3A1, 3A2, and 1A1 compared to SD rats. No significant difference was noted in other CYP isoforms. The mRNA levels of CAR were higher in DA rats than those in SD rats. In small intestine, the mRNA levels of CYP isoforms and nuclear receptors exhibited no significant strain differences. In addition, the activity of CYP3A in small intestinal microsome did not differ between SD and DA rats. Female DA rats exhibited higher mRNA levels of CYP3A1, 3A2, and 2B1 in the liver than female SD rats. In conclusion, the mRNA levels of CYP3A1 and 3A2 isoforms and CAR in the liver but not in the small intestines were different between DA and SD rats in both sexes.

Trace amine-associated receptor 1 displays species-dependent stereoselectivity for isomers of methamphetamine, amphetamine, and para-hydroxyamphetamine

The synthetic amines methamphetamine (METH), amphetamine (AMPH), and their metabolite para-hydroxyamphetamine (POHA) are chemically and structurally related to the catecholamine neurotransmitters and a small group of endogenous biogenic amines collectively referred to as the trace amines (TAs). Recently, it was reported that METH, AMPH, POHA, and the TAs para-tyramine (TYR) and beta-phenylethylamine (PEA) stimulate cAMP production in human embryonic kidney (HEK)-293 cells expressing rat trace amine-associated receptor 1 (rTAAR1). The discovery that METH and AMPH activate the rTAAR1 motivated us to study the effect of these drugs on the mouse TAAR1 (mTAAR1) and a human-rat chimera (hrChTAAR1). Furthermore, because S-(+)-isomers of METH and AMPH are reported to be more potent and efficacious in vivo than R-(-), we determined the enantiomeric selectivity of all three species of TAAR1. In response to METH, AMPH, or POHA exposure, the accumulation of cAMP by HEK-293 cells stably expressing different species of TAAR1 was concentration- and isomer-dependent. EC50 values for S-(+)-METH were 0.89, 0.92, and 4.44 microM for rTAAR1, mTAAR1, and h-rChTAAR1, respectively. PEA was a potent and full agonist at each species of TAAR1, whereas TYR was a full agonist for the rodent TAAR1s but was a partial agonist at h-rChTAAR1. Interestingly, both isomers of METH were full agonists at mTAAR1 and h-rChTAAR1, whereas both were partial agonists at rTAAR1. Taken together, these in vitro results suggest that, in vivo, TAAR1 could be a novel mediator of the effects of these drugs.