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A new, rapid, and sensitive assay for phospholipase A, utilizing commercially available [14C]phosphatidylethanolamine with 14C label in both palmitic acid moieties, was used to study phospholipase A release from perfused liver, hepatocytes, and intestinal cells from rats. Heparin triggered a prompt release of phospholipase A from perfused liver. Phospholipase A and triglyceride lipase were released from hepatocytes at a linear rate for 1 h and 30 min, respectively. Heparin (20 u/ml) doubled the release of phospholipase A and triglyceride lipase from hepatocytes. Colchicine (0.1 mM), but not puromycin (0.2 mM), inhibited basal and heparin-stimulated phospholipase A release by 40%. Since the amount of phospholipase A and triglyceride lipase released into the medium greatly exceeded intracellular activities, it is possible that secretion is coupled with intracellular conversion from inactive to active forms of the enzymes. Dibutyryl cyclic AMP (1 mM) inhibited phospholipase A (48%) and triglyceride lipase (82%) release from hepatocytes. Epinephrine, dexamethasone, and clofibrate inhibited release of triglyceride lipase but not phospholipase A. Phospholipase A activity of intestinal cells was greater than in hepatocytes, but neither heparin nor dibutyryl cyclic AMP affected phospholipase A release from intestinal cells. These results suggest that the liver is a major source of phospholipase A of postheparin plasma. The fact that dibutyryl cyclic AMP affects the release of these enzymes suggests an additional mechanism for hormonal regulation of lipid and lipoprotein metabolism.
G S Sundaram, and
K M Shakir, and
G Barnes, and
S Margolis
January 1977,
Biochimie,
G S Sundaram, and
K M Shakir, and
G Barnes, and
S Margolis
August 1966,
Biochimica et biophysica acta,
G S Sundaram, and
K M Shakir, and
G Barnes, and
S Margolis
January 1989,
Enzyme,
G S Sundaram, and
K M Shakir, and
G Barnes, and
S Margolis
January 1982,
Enzyme,
G S Sundaram, and
K M Shakir, and
G Barnes, and
S Margolis
January 1988,
Ukrainskii biokhimicheskii zhurnal (1978),
G S Sundaram, and
K M Shakir, and
G Barnes, and
S Margolis
June 1990,
Endocrinologia japonica,
G S Sundaram, and
K M Shakir, and
G Barnes, and
S Margolis
March 1973,
The Journal of biological chemistry,
G S Sundaram, and
K M Shakir, and
G Barnes, and
S Margolis
October 1969,
Hoppe-Seyler's Zeitschrift fur physiologische Chemie,
G S Sundaram, and
K M Shakir, and
G Barnes, and
S Margolis
May 1982,
Biochemical and biophysical research communications,
G S Sundaram, and
K M Shakir, and
G Barnes, and
S Margolis
January 1975,
Methods in enzymology,
