The metabolism and biosynthesis of (+/-)-o-octopamine and (+/-)-o-synephrine in the rat.
The metabolism of (+/-)-o-octopamine and (+/-)-o-synephrine by rats was studied quantitatively by a gas chromatography-mass spectrometry-selected ion monitoring (g.c.-m.s.-s.i.m.) method using deuterated internal standards. When o-octopamine was injected intraperitoneally into rats four metabolites were excreted in the urine: (i) unconjugated o-hydroxymandelic acid (OHMA) (16%), (ii) unconjugated o-hydroxyphenylglycol (OHPG) (4.5%), (iii) an acid-hydrolysable conjugate of OHPG (28%) and (iv) unconjugated o-octopamine (10%). When o-synephrine benzoate was similarly administered six metabolites were excreted in urine: (i) unconjugated OHMA (13.5%), (ii) unconjugated OHPG (3.3%), (iii) an acid-hydrolysable conjugate of OHPG (15.6%), (iv) unconjugated o-synephrine (10%), (v) an acid-hydrolysable conjugate of o-synephrine (8.5%) and (vi) unconjugated o-octopamine (0.3%). Adult rats normally excreted OHMA (1.0 micrograms day-1) but OHPG, o-octopamine and o-synephrine could not be detected in urine. After the administration of a monoamine oxidase inhibitor, unconjugated o-octopamine (0.3 micrograms day-1) was excreted in urine but OHPG and o-synephrine could not be detected. o-Tyramine given to rats afforded urinary o-octopamine (75 ng day-1) and this was increased 10-fold upon co-administration of a monoamine oxidase inhibitor and o-tyramine.
D000818:Animals; D008401:Gas Chromatography-Mass Spectrometry; D006018:Glycols / Q000652:urine; D007490:Iproniazid / Q000494:pharmacology; D008297:Male; D008333:Mandelic Acids / Q000652:urine; D009655:Octopamine / Q000096:biosynthesis / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013578:Synephrine / Q000096:biosynthesis / Q000378:metabolism*; D014439:Tyramine / Q000494:pharmacology
D006018:Glycols; D008333:Mandelic Acids; D009655:Octopamine; C024038:2-hydroxymandelic acid; C028434:2-synephrine; C038985:2-hydroxyphenyl glycol; C028435:2-octopamine; D007490:Iproniazid; D013578:Synephrine; D014439:Tyramine