Stimulatory release of hepatic lipase activity from cultured rat hepatocytes by sodium orthovanadate: rapid increase in cyclic adenosine monophosphate content.
The release of hepatic triacylglyceride lipase [EC 3.1.1.3] has been examined in isolated hepatocytes in primary culture. The stimulatory release of activity from the hepatocytes into the medium by sodium orthovanadate (vanadate) was observed in a time- and dose-dependent manner. However, insulin failed to have this stimulatory action. Moreover, vanadate rapidly increased the cyclic adenosine monophosphate (cyclic AMP) content in hepatocytes in a time- and dose-dependent manner. The treatment of hepatocytes with H-89, which is a potent cyclic AMP-dependent protein kinase inhibitor, decreased the stimulatory release of hepatic lipase activity by vanadate. The vanadate-stimulated release of the enzyme activity was suppressed by uncouplers. In addition, the incorporation of [3H]leucine into protein was increased in the presence of vanadate. Under the marked inhibition of protein synthesis by cycloheximide, vanadate still showed a full effect on the release of the enzyme activity. These results suggest that the vanadate-stimulated release of hepatic lipase activity from the cultured hepatocytes is associated with a rapid increase in intracellular cyclic AMP content, probably due to an activation of cyclic AMP-dependent protein kinase which requires a metabolic energy process rather than an elevation in enzyme molecule synthesis.
Morita
T
T
Department of Biochemistry, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Japan.
Sakata
K
K
Kanagawa
A
A
Ueki
H
H
D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D007930:Leucine / Q000378:metabolism; D008049:Lipase / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D047428:Protein Kinase Inhibitors; D051381:Rats; D017208:Rats, Wistar; D013449:Sulfonamides; D014638:Vanadates / Q000494:pharmacology*
D007328:Insulin; D007546:Isoquinolines; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; D014638:Vanadates; D003513:Cycloheximide; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D008049:Lipase; D007930:Leucine; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide