Regulation of apolipoprotein A-I synthesis in lymph-drained rats.
The effect of lymph diversion on plasma apolipoprotein A-I levels was studied. In lymph fistula rats apolipoprotein A-I levels in plasma stayed constant in spite of a loss of an equivalent of one-half plasma pool of apolipoprotein A-I per day through the lymph fistula. This indicates that synthesis of apolipoprotein A-I increases or that catabolism of apolipoprotein A-I decreases in a compensatory manner as intestinal apolipoprotein A-I is diverted. By using incorporation of [3H]leucine into newly synthesized apolipoprotein A-I it was shown that 2.6-times as much [3H]leucine was incorporated into apolipoprotein A-I in thoracic duct drained animals compared to controls. In experiments in which 125I-labeled HDL was injected intravenously into rats, it was shown that catabolism of HDL and apolipoprotein A-I was not decreased in lymph-drained rats. These data thus suggest that an increased synthesis of apolipoprotein A-I occurs when the intestinal contribution of apolipoprotein A-I diminishes. This is probably due to an increase in liver protein synthesis.
D000818:Animals; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000096:biosynthesis* / Q000097:blood; D001057:Apolipoproteins E / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D008075:Lipoproteins, HDL / Q000378:metabolism; D008196:Lymph / Q000502:physiology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D001057:Apolipoproteins E; D008075:Lipoproteins, HDL; D007930:Leucine