title: Effect of sodium taurodeoxycholate, CaCl2 and albumin on the action of pancreatic lipase on droplets of trioleoylglycerol and the release of lipolytic products into aqueous media.
abstract: 1. Effects of various substances on the activity of pancreatic lipase and on the release of lipolytic products into aqueous media were studied with droplets of trioleoylglycerol suspended from a membrane filter at the top of a flow-through chamber. The droplets were perifused for 7 min with a commercial preparation of pancreatic lipase in 0.15 M NaCl solution at pH 6.5 and then perifused for 60 min with lipase-free media, either 0.15 M NaCl at pH 6.5 or basal medium at pH 7.4 (70 mM sodium barbital) containing different additives. 2. About 6% of the trioleoylglycerol in droplets was hydrolyzed during the perifusion with lipase. Another 15% was hydrolyzed in 30 min, but none thereafter, when the droplets were perifused with 0.15 M NaCl alone. The rate of hydrolysis was doubled and prolonged when droplets were perifused with basal medium at pH 7.4. Lipolytic products formed at pH 7.4 were 62% oleic acid, 20% monooleoylglycerol and 18% dioleoylglycerol, yet only 4% of the lipolytic products were released into the perifusate. 3. Sodium taurodeoxycholate (TDC) (17 mM ) added to basal medium increased 18 x the amount of lipolytic products released into the perifusate but increased lipolysis only 13%. The molar ratio of oleic acid to monooleoylglycerol in the perifusate was 5.7 during the first 30 min and 4.0 during the last 30 min. 4. Ca2+ (3.3 mM) added to basal medium increased lipolysis 87% but did not affect the amount (4%) of lipolytic products released into the perifusing medium. 5. TDC and Ca2+ added to basal medium produced the largest increase in lipolysis, with 59% of trioleoylglycerol hydrolyzed in 15 min and 91% in 60 min. The amount of lipolytic products released into the perifusing medium, however, was not increased above that released into medium containing TDC alone. 6. Serum albumin (0.6 mM) and Ca2+ added to basal medium increased 14 x the amount of lipolytic products released into the perifusate without affecting the basal lipolytic rate. Albumin, however, suppressed by 40% the stimulatory effect of Ca2+ on pancreatic lipase activity.
authors.affiliation: Laboratory of Cellular and Development Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892.
authors.forename: R O
authors.initials: RO
authors.lastname: Scow
mesh_terms: D000418:Albumins / Q000494:pharmacology*; D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology*; D003840:Deoxycholic Acid / Q000031:analogs & derivatives*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008049:Lipase / Q000378:metabolism*; D008066:Lipolysis; D010179:Pancreas / Q000201:enzymology*; D013552:Swine; D013657:Taurodeoxycholic Acid / Q000494:pharmacology*; D014304:Triolein / Q000378:metabolism*
chemical_list: D000418:Albumins; D003840:Deoxycholic Acid; D014304:Triolein; D013657:Taurodeoxycholic Acid; D008049:Lipase; D002122:Calcium Chloride