Regulation of lipoprotein lipase by dibutyryl cAMP, cholera toxin, Hepes and heparin in F1 heart-cell cultures.
Regulation of lipoprotein lipase was studied in mesenchymal rat heart-cell cultures. Treatment of the cultures with dibutyryl cyclic AMP or with cholera toxin resulted in an increase in LPL activity and a comparable increase in LPL mRNA. When the cells were exposed to 100 mM Hepes for 24 h, total enzyme activity rose 2-fold and LPL mRNA increased 2.4-fold. After 72 h, there was a 3-fold increase in LPL mRNA and a 4-fold rise in cellular LPL activity, while medium activity increased 20-fold. Exposure of the cultures to heparin for 24 h resulted in a 3.2-fold increase in total activity and a 36-fold increase in medium activity. This increase was not accompanied by any rise in LPL mRNA. Addition of actinomycin D to control dishes for 24 h resulted in a 33% reduction in LPL mRNA and a 43% reduction in enzyme activity. These values were 71% and 56%, respectively, in Hepes-treated cells, indicating that no stabilization of LPL mRNA occurred under these conditions. It can be concluded that in mesenchymal rat heart-cells in culture cAMP and cholera toxin upregulate lipoprotein lipase at the level of transcription. The increase in LPL activity after 24 h exposure to Hepes could be compatible with transcriptional regulation, while exposure to heparin is not accompanied by a change in LPL mRNA.
Friedman
G
G
Department of Medicine, Hadassah-University Hospital, Jerusalem, Israel.
Reshef
A
A
Ben-Naim
M
M
Leitersdorf
E
E
Stein
O
O
Stein
Y
Y
D000818:Animals; D000831:Animals, Newborn; D003994:Bucladesine / Q000494:pharmacology*; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology*; D003609:Dactinomycin / Q000494:pharmacology; D006531:HEPES / Q000494:pharmacology*; D006493:Heparin / Q000494:pharmacology*; D008071:Lipoprotein Lipase / Q000235:genetics / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D012313:RNA / Q000235:genetics; D051381:Rats; D014158:Transcription, Genetic
D003609:Dactinomycin; D012313:RNA; D003994:Bucladesine; D006493:Heparin; D002772:Cholera Toxin; D008071:Lipoprotein Lipase; D006531:HEPES