title: [Catabolism of carnitine: products of carnitine decarboxylase and carnitine dehydrogenase in vivo].
abstract: 1) Rats and mice were given large oral or subcutaneous doses of (-)-L-, (+)-D- and DL-carnitine (5 mg/g body weight). The carnitine metabolites, beta-methylcholine and acetonyltrimethylammonium, were isolated from the urine by special methods, and determined as their characteristic derivatives (2,4-dinitrophenylhydrazone and butyric ester) by thin-layer chromatography or photometry. 2) beta-Methylcholine, the product of carnitine decarboxylase, was not excreted, even when animals were heavily dosed with both carnitine isomers, with or without starvation. 3) After the administration of (+)-D- and DL-carnitine, both species excreted acetonyltrimethylammonium, which is already known as the spontaneous decarboxylation product of dehydrocarnitine (product of carnitine dehydrogenase) in bacteria. Injection of 0.71 mmol (+)-D-carnitine resulted in the excretion of 5.0 mumol (average) acetonyltrimethylammonium per mouse during the 48 h post injection. Under the same conditions, rats produced up to 40 mumol acetonyltrimethylammonium. The ratio of excreted acetonyltrimethylammonium to injected (+)-D-carnitine depended on the method of administration and the dose. 4) Production of the pharmacologically active (+)-acetyl-L-beta-methylcholine is not to be expected, following high exogenous doses of (-)-L-carnitine or (-)-acetyl-L-carnitine. The chief metabolites are trimethylamine, trimethylamine oxide and gamma-butyrobetaine (this journal 361, 1059), and both the (-)-L-carnitine pool and exogenous (-)-L-carnitine are dehydrogenated or decarboxylated only to a very small extent, if at all. When DL-carnitine is used therapeutically, the formation of acetonyltrimethylammonium must be taken into account.
mesh_terms: D000284:Administration, Oral; D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D000818:Animals; D002262:Carboxy-Lyases / Q000378:metabolism*; D002331:Carnitine / Q000008:administration & dosage / Q000378:metabolism*; D002794:Choline / Q000031:analogs & derivatives / Q000652:urine; D002855:Chromatography, Thin Layer; D005260:Female; D051379:Mice; D000644:Quaternary Ammonium Compounds / Q000652:urine; D051381:Rats; D013237:Stereoisomerism
chemical_list: D000644:Quaternary Ammonium Compounds; C017506:methylcholine; D000429:Alcohol Oxidoreductases; C019842:carnitine dehydrogenase; D002262:Carboxy-Lyases; C019841:carnitine decarboxylase; C027699:acetonyltrimethylammonium; D002794:Choline; D002331:Carnitine
vernacular_title: Kataboler carnitinstoffwechsel: reaktionsprodukte der carnitin-decarboxylase und der carnitin-dehydrogenase in vivo.