Biphasic effects of glucagon and cyclic AMP on the synthesis and secretion of lipids by rat hepatocytes.
Cultured rat hepatocytes were preincubated with glucagon or a cyclic AMP analogue for up to 24 h and lipid synthesis and secretion were determined during the next 2 h. Glucagon or cyclic AMP did not change the incorporation of choline or glycerol into phosphatidylcholine, or choline into sphingomyelin, in the cells after 0-12 h of preincubation. After 12 h these incorporations were increased. Incorporations into hepatic lysophosphatidylcholine were decreased after preincubation with glucagon or cyclic AMP for 0-12 h, but by 24 h they increased. There was no change in the lysophosphatidylcholine in the medium after preincubation with glucagon or cyclic AMP for up to 6 h, but increases occurred after preincubation from 12 to 24 h. The secretion of triacylglycerol was decreased after preincubation for 0-1 h, but it returned to control values after 4 h. After preincubation for 18-24 h the incorporation of glycerol into secreted triacylglycerol was increased. The results are discussed in relation to the control of lipid metabolism in starvation and diabetes.
Hermier
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D
Department of Biochemistry, Faculty of Medicine, University of Alberta, Edmonton, Canada.
Hales
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P
Brindley
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DN
D000818:Animals; D001692:Biological Transport; D002794:Choline / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology*; D005934:Glucagon / Q000494:pharmacology*; D050356:Lipid Metabolism; D008055:Lipids / Q000096:biosynthesis*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D014280:Triglycerides / Q000378:metabolism
D008055:Lipids; D010743:Phospholipids; D014280:Triglycerides; D005934:Glucagon; D000242:Cyclic AMP; D002794:Choline