title: Surplus acylcarnitines in the plasma of starved rats derive from the liver.
abstract: The method used here to assess the contribution of liver to plasma acylcarnitine is based on the idea that in rat, shortly after administration of [3H]butyrobetaine the [3H]carnitine appearing in the plasma derives from the liver and so does the acyl moiety of [acyl-3H] carnitine. In the perchloric acid extracts of plasma and liver, the ester fraction of total carnitine was determined by enzymatic analysis and that of [3H]carnitines was determined by high performance liquid chromatography. The ester fraction of total carnitine in the plasma of fed rats was 32.6% while that of [3H]carnitines was 67.9%, 1 h following injection of [3H]butyrobetaine. For 48 h starved rats the equivalent values were 54.2 and 84.0%, respectively. 24 h after the administration of [3H]butyrobetaine, the ester content became the same in the total and [3H]carnitines. That the newly synthesized carnitine was more acylated (67.9 versus 32.6%, fed) indicates that liver exports acyl groups with carnitine as carrier. The observation that the ester fraction in the newly synthesized plasma carnitine increased with fasting (84.0 versus 67.9%) indicates that the surplus plasma acylcarnitine in fasting ketosis derives from the liver. Perfused livers, however, released carnitine with the same ester content (60-61%) whether they were from fed or fasted animals. Probably, the increased plasma [acylcarnitine] in fasting develops not by an increased ester output from the liver but by an altered handling in extrahepatic tissues.
authors: Institute of Biochemistry, University Medical School, Pecs, Hungary.
authors: A
authors: A
authors: Sandor
authors: J
authors: J
authors: Cseko
authors: G
authors: G
authors: Kispal
authors: I
authors: I
authors: Alkonyi
mesh_terms: D000215:Acylation; D000818:Animals; D001622:Betaine / Q000031:analogs & derivatives / Q000378:metabolism; D002331:Carnitine / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D013217:Starvation / Q000097:blood / Q000378:metabolism*
chemical_list: D001622:Betaine; C002889:gamma-butyrobetaine; D002331:Carnitine