A rapid effect of thyroxine on accumulation of diacylglycerols and on activation of protein kinase C in liver cells.
L-Thyroxine rapidly stimulated the accumulation of diacylglycerols in isolated hepatocytes and in liver when lipids were prelabeled with [14C]oleic acid or with [14C]CH3COONa. Perfusion of the liver of hypothyroid animals with L-thyroxine-containing solution or incubation of liver fragments with the hormone increased the content of diacylglycerols in the liver cells. The increase in [14C]diacylglycerol level in the liver cells was accompanied by a decrease in the level of [14C]phosphatidylcholine, whereas contents of other 14C-labeled phospholipids, such as phosphatidylethanolamine, sphingomyelin, lysophosphatidylcholine, phosphatidylinositol (PtdIns), phosphatidylinositol-4-phosphate (PtdIns4P), and phosphatidylinositol-4,5-bis-phosphate (PtdIns(4,5)P2), and of 14C-labeled fatty acids were the same as in the control. The L-thyroxine-induced accumulation of diacylglycerols in hepatocytes was not affected by neomycin but was inhibited by propranolol. Incubation of hepatocytes prelabeled with [14C]oleic acid with L-thyroxine and ethanol (300 mM) was accompanied by generation and accumulation of [14C]phosphatidylethanol that was partially suppressed by 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7). L-Thyroxine was responsible for the translocation of protein kinase C from the cytosol into the membrane fraction and for a many-fold activation of the membrane-bound enzyme. D-Thyroxine failed to affect the generation of diacylglycerols in hepatocytes and the activity of protein kinase C.
Kavok
N S
NS
Institute of Biology, Kharkov National University, Kharkov, 61077 Ukraine.
Krasil'nikova
O A
OA
Sidorkina
O M
OM
Babenko
N A
NA
D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D004075:Diglycerides / Q000378:metabolism*; D004789:Enzyme Activation; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D008297:Male; D010743:Phospholipids / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013974:Thyroxine / Q000494:pharmacology*
D004075:Diglycerides; D010743:Phospholipids; D011493:Protein Kinase C; D013974:Thyroxine