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1.
Bengt Borgström 《Lipids》1993,28(5):371-375
The long-chain phosphatidylcholine/sodium cholate aqueous system as substrate for human pancreatic phospholipase A2 (PLA2) was investigated. At a constant phosphatidylcholine (PC) concentration of 8 mM, the enzyme activity increased with a decrease
in cholate (C) concentration up to a PC/C ratio of approximately 0.8 and then rather abruptly decreased to lower values at
a ratio above 1.5. At ratios between 0.8 and 1.5, an increasing lag phase in the PLA2 activity was seen, indicating a progressive decrease in substrate availability to the enzyme. Reaction mixtures with a PC/C
ratio of up to 0.67 were optically clear solutions composed of mixed bile salt/PC micelles of increasing mixed micellar aggregate
size. Ratios between 0.67 and 1.5 were characterized by an increase in turbidity (at 330 and 450 nm) due to increasing formation
of vesicles or liposomes. Above a PC/C ratio of 1.5, a sharp increase in turbidity was seen due to increasing formation of
bilayer structures other than vesicles. Pure vesicles obtained by dialysis of mixed micellar solutions were not hydrolyzed
by the enzyme. Addition of bile salts reversed the inhibition which was accompanied by a decrease in turbidity. Phosphatidylcholine
was preferred as substrate for human PLA2 when present in large mixed disc-like bile salt micelles. Vesicular or other types of lamellar liquid-crystalline phases
of long-chain phosphatidylcholine did not serve as substrate for PLA2. 相似文献
2.
The regulation of cholesterol ester hydrolase activity by female sex hormones was studied in cytosolic preparations from female
rat liver. The investigation was undertaken in order to determine whether a reduction in the enzyme activity might be responsible
for the increased content of esterified cholesterol found in rat liver after estradiol or progesterone treatments. The single
injection of estradiol (0.75 mg/100 g) or progesterone (1.50mg/100g) produced respectively significant decreases and increases
in sterol hydrolase activity. Both opposite effects were noted after a similar lag period of 3–4 hr and were of short duration.
No alterations were observed in rats receiving short-term treatments. When hormones were added to the incubation medium, the
activity of cholesterol ester hydrolase decreased progressively with increasing concentrations of hormones. Kinetic studies
demonstrate that both estradiol and progesterone compete with the substrate (cholesteryl oleate) for the active center. The
findings of the present paper exclude a direct relationship between hepatic hydrolytic activity and lipid deposition. However,
they provide evidences that female sex hormones act as modulatory agents of the hydrolysis of cholesteryl esters in rat liver
cytosol and suggest that other factors besides competitive inhibition are involved in such regulatory effects. 相似文献
3.
The enzyme(s) present in acetonedried powder of rat and rabbit aortas, which catalyzes the synthesis and hydrolysis of cholesteryl ester, was purified partially by acid precipitation, acetone fractionation, 0-(diethylaminoethyl) cellulose chromatography, and Sephadex G-100 filtration. The synthetic activity was purified by 120-fold (rat) and 140-fold (rabbit). Purification of hydrolytic activity was 90-fold (rat) and 103-fold (rabbit). Cholesteryl ester hydrolase activity was separated from nonspecific, esterase by column chromatography. Both synthetic and the hydrolytic activities are apprently the functions of one enzyme. The mol wt of the enzyme was estimated to be 140,000 dalton as determined by Sephadex G-200 gel filtration. The extracts of the acetone-dired powders of aortas of both species contained an inhibitor of synthetic activity. The inhibitor was nondialyzable and was precipitated at pH 5.7 Both activities were found to be fairly nonspecific with regard to sterol and fatty acids. With oleic acid, the relative rates of sterol ester synthesis were: cholesterol, 100; cholestanol, 94; desmosterol, 35; corprostanol, 24; ergosterol, 20; and β-sitosterol, 19. Epicholesterol was not esterified. Oleic acid was most active in cholesteryl ester synthesis, the relative rates being: oleic>linoleic>arachidonic>palmitic>stearic>butyric. The rate of hydrolysis was maximum with cholesteryl linoleate followed by oleate, linolenate, palmitate, stearate and laurate in decreasing order. 相似文献
4.
The hydrolysis of conjugated bile acids by cholylglycine hydrolase (EC 3.5.1.24) using the standard procedure for a commercial
enzyme preparation was found to be incomplete, as judged by the use of 24-14C-taurocholic acid as a tracer. A method is proposed that incorporates the nonionic detergent Triton X-100 into the reaction
mixture to achieve almost complete hydrolysis. It is proposed that the observed enhancement of enzyme activity is due to the
formation of micelles by the detergent. 相似文献
5.
The regulation of neutral cholesterol ester hydrolase activity by changes in its phosphorylation state was studied in rat
liver microsomes. Treatment with cAMP-dependent protein kinase resulted in increased enzyme activity, which was further enhanced
by the addition of cAMP and MgATP. Consistent activations were also achieved with MgCl2 and MgATP, the magnesium effect being abolished by ethylenediaminetetraacetic acid and adenosine triphosphate. Cholesterol
ester hydrolase was activated twofold by free calcium and Ca2+/calmodulin; this latter effect was blocked by the chelator ethyleneglycol-bis(β-aminoethyl ether)N,N,N′,N′-tetraacetic acid and the calmodulin antagonist trifluoperazine. The phosphatase inhibitors pyrophosphate and glycerophosphate
led to marked and dose-dependent increases in esterase activity, whereas okadaic acid elicited no effect. Furthermore, pyrophosphate
and okadaic acid did not change the increases in enzyme activity promoted by Ca2+, Ca2+/calmodulin, Mg2+ and MgATP. Cholesterol ester hydrolase was inactivated in a concentration-dependent manner by nonspecific alkaline phosphatases.
In cAMP-dependent protein kinase/cAMP- or Ca2+/calmodulin-activated microsomes, a time-dependent loss of activation in cholesteryl oleate hydrolysis was caused by alkaline
phosphatase. These findings suggest that microsomal cholesterol ester hydrolase is activated through cAMP and Ca2+/calmodulin phosphorylation, whereas enzyme deactivation is dependent on phosphatase action. 相似文献
6.
Short-term activation of microsomal cholesterol ester hydrolase by glucagon, cAMP analogues, and vasopressin in isolated rat
hepatocytes is described. Glucagon led to a dose-and time-dependent activation of cholesteryl oleate hydrolysis, but values
returned to basal levels within 120 min. Exposure of isolated hepatocytes to 0.5 mM concentrations of dibutyryl-cAMP or 8-[4-chlorophenylthio]-cAMP,
or 25 μM forskolin caused persistent activation of cholesterol ester hydrolase activity after a lag period of 30 min. The
three agents resulted in early marked intracellular accumulation of cAMP that declined progressively, and moderate and sustained
reductions in the diacylglycerol content. The actions of glucagon on hepatocytes were inhibited by pretreatment of cells with
10 nM [8-arginine] vasopressin. Vasopressin elicited a consistent and sustained increase in cholesterol ester hydrolase activity
and diacylglycerol without affecting cAMP while reducing the effect of glucagon on cAMP. Furthermore, the effects of glucagon
and vasopressin on the activation of cholesterol ester hydrolase were not additive despite the similarity of their stimulation
of diacylglycerol formation. Blockade of vasopressin-mediated activation of cholesterol ester hydrolase and diacylglycerol
content were induced by excess prazosin. These data suggest that stimulation of microsomal cholesterol ester hydrolase in
isolated liver cells may involve at least two signal transduction systems. 相似文献
7.
Neutral cholesteryl ester hydrolase activity (EC 3.1.1.13) present in microsomes isolated from lactating rat mammary glands
was found to be inhibited by a factor (or factors) occurring in the cytosolic fraction of male rat liver. The inhibitor was
heat-labile, non-dialyzable, destroyed by proteolysis, and was stable following preparation of an acetone/diethyl ether powder
of the cytosolic fraction. The protein also inhibited the activity of hormone-sensitive lipase (HSL) (from bovine adipose
tissue) and esterase fromCandida cylindracea, but seemed to be more active against the neutral hydrolase found in rat liver microsomes. For the mammary gland microsomal
cholesteryl ester hydrolase, the extent of the inhibitory effect was dependent on the concentration of the cytosolic protein,
50% inhibition being achieved by about 100 μg of cytosolic protein, and on the method of initiating the enzyme assay. Kinetic
analysis indicated that, under circumstances where the reaction was initiated by the addition of substrate, the inhibition
was characterized as “uncompetitive”. When an inhibitor/substrate complex was allowed to form in the absence of enzyme, an
element of “competitive” inhibition was introduced into the reaction. Food withdrawal reducted the activity of the inhibitor
in live by 56%, but activity was fully restored by short-term re-feeding. In contrast, feeding a diet high in fat led to a
34% increase in activity. The present findings suggest that the inhibitory factor(s) may be involved in the regulation of
the hydrolysis of cholesteryl esters in the liver and also in other cell types. 相似文献
8.
Ion-exchange chromatography and preparative isoelectric focusing (PIEF) were compared to produce a stable rat liver lysosomal
cholesteryl ester hydrolase of high specific activity. The PIEF purification method proved to be more rapid and easier to
perform. PIEF purification involved the following steps: i) osmotic shock of the lysosome fraction, ii) (NH4)2 SO4 precipitation (10–70%, w/v), iii) Sepharose CL-6B gel filtration, and iv) PIEF. The enzyme was purified 60–120-fold with
a yield of 2–4%. The activity of the purified enzyme was best restored by stabilizing with a 0.5% (w/v) albumin solution.
The purified enzyme produced one major band on SDS-polyacrylamide gel electrophoresis having a MW of 58,500 daltons. Gel filtration
showed a MW of 58,000 daltons. The optimum pH of the enzyme was 4.5, and the isoelectric point was 6.0–6.2. The specific activity
of hydrolysis of cholesteryl oleate and triolein increased by similar rates during purification. 相似文献
9.
The utility of 2-hydroxypropyl-β-cyclodextrin for increasing the sensitivity of assays for the microsomal acyl-CoA:cholesterol
acyltransferase, and the acid lysosomal and the neutral microsomal and cytosolic cholesterol ester hydrolase activity was
studied in rat hepatocytes. Enzyme assays, at optimal concentrations of cyclodextrin, were validated by assessing: (i) linearity
of product formation with incubation time and protein amount, and saturation with substrate, and (ii) the effect of treatments
of cells or of subcellular fractions on enzyme activities. Delivery of cholesterol dissolved in 2-hydroxypropyl-β-cyclodextrin
to the acyl-CoA:cholesterol acyltransferase assay mixture raised the enzyme activity more than 8-fold and was twice that measured
when cholesterol was added in Triton WR-1339. 2-Hydroxypropyl-β-cyclodextrin itself was partially effective, apparently by
making endogenous cholesterol more accesible to the enzyme. Inclusion of 2-hydroxypropyl-β-cyclodextrin in cholesterol ester
hydrolase assays using standard micellar substrates doubled the activity estimated in lysosome and microsome preparations
and enhanced the cytosolic cholesterol esterase activity by about 50%. Differences in the catalytic activity of acyl-CoA:cholesterol
acyltransferase and cholesterol ester hydrolases caused by treatment of hepatocytes with compound 58-035 or 25-hydroxycholesterol,
or of subcellular fractions with NaF, were maintained when enzymes were assayed with cyclodextrin. The results indicate that
2-hydroxypropyl-β-cyclodextrin is a suitable vehicle for delivering cholesterol to acyl-CoA:cholesterol acyltransferase and
enhances the sensitivity of standard assays of the enzymes governing the intrahepatic hydrolysis of cholesteryl esters. 相似文献
10.
The regulation of cholesterol uptake and secretion by acylcoenzyme A:cholesterol acyltransferase (ACAT) was investigated in
the human intestinal cell line, CaCo-2. A new ACAT inhibitor, PD128042 (CI-976), was first characterized. The addition of
the fatty acid anilide to membranes prepared from CaCo-2 cells inhibited ACAT activity without altering the activities of
HMG-CoA reductase, fatty acid Co-A hydrolase, or triglyceride synthetase. PD128042 was a competitive inhibitor of ACTA with
50% inhibition occurring at a concentration of 0.2 μg/mL. When added to the medium of CaCo-2 cells at a concentration of 5
μg/mL, PD128042 inhibited oleate incorporation into cholesteryl oleate by 92% and increased oleate incorporation into triglycerides
and phospholipids by 51% and 38%, respectively. After incubating CaCo-2 cells with the ACAT inhibitor, the rate of newly synthesized
cholesterol decreased by 75% and membranes prepared from these cells contained significantly less HMG-CoA reductase activity.
PD128042 significantly decreased the basolateral secretion of newly synthesized cholesteryl esters without affecting the secretion
of newly synthesized triglycerides or phospholipids. The inhibitor decreased the esterification of labeled exogenous cholesterol
which was taken up by the cell from bile salt micelles. Moreover, after 16 hr of ACAT inhibition, less labeled unesterified
micellar cholesterol was associated with the cell. The esterification of cholesterol in CaCo-2 cells plays an integral role
in the uptake of cholesterol through the apical membrane and its eventual secretion at the basolateral membrane. 相似文献
11.
Kathleen M. Botham 《Lipids》1991,26(11):901-906
An acid cholesteryl ester hydrolase activity associated with a fraction containing mitochondria and lysosomes from rat lactating
mammary glands was found to have a pH optimum of 5.0. Its sedimentation pattern was closely related to that of the lysosomal
enzyme markers acid phosphatase and β-glucuronidase, suggesting that the activity is associated with the lysosomes. The enzyme
was strongly inhibited by Cu2+, but was inhibited little by other divalent metal ions. Acid cholesteryl ester hydrolase activity was almost completely abolished
byp-hydroxymercuribenzoate, but this effect was reversed in the presence of an equimolar concentration of reduced glutathione
(GSH), indicating that the enzyme requires free sulfhydryl groups for activity. These properties are similar to those of acid,
lysosomal cholesteryl ester hydrolases found in other tissues. Acid cholesteryl ester hydrolase activity was 8–14 fold higher
in mammary tissue from lactating as compared to virgin rats. Neutral cholesteryl ester hydrolase activities associated with
the microsomal and cytosolic subcellular fractions were also increased in lactating glands, but to a lesser extent. In addition,
a 2-fold increase in the activities of both the acid and microsomal neutral enzymes was seen during the first few days of
lactation, while the cytosolic neutral activity remained constant. These results suggest that mammary gland cholesteryl ester
hydrolases have a role in the regulation of cholesterol metabolism in mammary cells, and in the provision of cholesterol for
secretion into milk. 相似文献
12.
George V. Vahouny Robert Tombes Marie M. Cassidy David Kritchevsky Linda L. Gallo 《Lipids》1980,15(12):1012-1018
Mixed micelles were prepared containing combinations of either taurocholate or taurochenodeoxycholate, monoolein, oleic acid,
dioleylphosphatidylcholine (lecithin) and cholesterol. These were incubated with commercial bile-acid-sequestering resins,
cholestyramine and DEAE-Sephadex, or various dietary fibers and fiber components including wheat bran, cellulose, alfalfa,
lignin and 2 viscosity grades of guar gum. Binding was determined as the difference between the radioactivity of each micellar
component added and that recovered in the centrifugal supernatant after incubation. In general, the extent of bile salt sequestration
was characteristic and reproducible for each bile salt, and was largely unaffected by the presence of one or more additional
components of the micellar mixture, including the other bile salt. Cholestyramine bound 81–92% of the bile salts and 86–99%
of the phospholipid and cholesterol present in micelles. DEAE-Sephadex sequestered only 49% of the taurocholate and 84% of
the taurochenodeoxycholate, but completely removed all of the phospholipid and cholesterol from micelles containing either
bile salt. Among the dietary fibers, guar gum of either viscosity bound between 20–38% of each micellar component, whereas
lignin, alfalfa, wheat bran and cellulose were progressively less effective in sequestratin of individual components of mixed
micelles. The extent of sequestration of micellar components by these resins and fibers is reasonably correlated with the
effects of these same materials on lymphatic absorption of lipids and to their suggested hypocholesteremic properties. 相似文献
13.
Fluorescent esters containing pyrenedecanoic acid (P10) or pyrenebutanoic (P4) acid (P4cholesterol, P10cholesterol, P4- and P10-containing triacylglycerols) were synthesized and used as substrates for human pancreatic carboxylic ester hydrolase and
bile salt-stimulated lipase from human milk. Both enzymes were purified by immunoaffinity chromatography. All fluorescent
pyrene derivatives were hydrolyzed by pancreatic carboxylic ester hydrolase and bile salt-stimulated lipase, but at different
rates. The hydrolytic rates of the “short” acyl esters (P4-containing esters) were higher than those of the “long” ones (P10-containing esters). Conditions were optimized for sensitivity of the assay using fluorescent cholesteryl esters. The pH optimum
was 7.5–8.0. Sodium cholate exhibited a stronger activating effect than taurocholate or taurodeoxycholate (maximal activation
was achieved with 5 mmol/L cholate and with a molar ratio cholesteryl ester/cholate around 1∶10). Both pancreatic carboxylic
ester hydrolase and bile salt-stimulated lipase from milk were strongly inhibited by the other amphiphiles tested, namely
phosphatidylcholine and Triton X-100, and were inactivated by low concentrations (10 μmol/L) of the serine-reactive diethyl-paranitrophenyl
phosphate (E600). Both enzymes were strongly inhibited by relatively low concentrations of plasma low density lipoproteins. These studies
indicate that the fluorescent esters containing pyrene fatty acids can be used as substrates for assaying and investigating
the properties of pancreatic carboxylic ester hydrolase as well as bile salt-stimulated lipase from milk. 相似文献
14.
Cholesteryl ester hydrolase was assayed in adrenal homogenates from mature female rats fed a control (corn oil-containing)
or essential fatty acid (EFA)-deficient diet. Cholesteryl ester of 16∶0, 18∶0, 18∶1, 18∶2(n−6), 20∶4(n−6) and 22∶4(n−6) were
used as substrates. In control rats, the unsaturated esters were hydrolyzed more rapidly than the saturated esters and cholesteryl
arachidonate was the preferred substrate of the six investigated; cholesteryl oleate elicited the highest activity in the
deficient group. Polyunsaturated esters were hydrolyzed at a significantly lower rate by homogenates from EFA-deficient rats
than by those from control animals. The esters of 18∶1, 18∶2(n−6) and 20∶4(n−6) were hydrolyzed more extenstively in relation
to their concentrations in adrenal tissue than were cholesteryl esters of 16∶0, 18∶0 and 22∶4(n−6). This difference was more
pronounced in control than in EFA-deficient rats. No simple relationship of adrenal cholesteryl ester hydrolase activity to
ester fatty acid structure or to nutritional essentiality was evident. 相似文献
15.
Labeled cholesterol and its esters were injected via the portal vein into bile duct-cannulated rats, subsequent to a 7 week
regimen of either 5% safflower oil or 5% beef tallow in a hypercholesterolemic diet. Analysis of bile collected over a 6 hr
period from the safflower group showed 8.6% higher output of bile acids, 13.6% higher conversion of3H-cholesterol to bile acids and 40% higher conversion of [4-14C]cholesteryl oleate to bile acids than bile collected from the tallow group. During the 1st hr conversion of both oleyl and
linoleyl esters of14C-cholesterol to bile acids was much slower than conversion of the free3H-cholesterol to bile acids, thus eliminating these esters as preferred substrate for bile acid formation. However at 6 hr
two-thirds of the injected14C of oleyl ester was recovered in the liver, and about half of this was in the form of free cholesterol. Thus cholesterol
ester hydrolase, though inhibited by dietary cholesterol, evidently did not impose limitations on formation of free cholesterol
for subsequent oxidation reactions. Specific radioactivities were of doubtful significance because of uncertainities as to
“active” pool size. The data suggest that dietary linoleate exerts its hypocholesterolemic effect in some manner other than
ester formation and that its point of action involves stimulation of cholesterol oxidation to bile acids.
Journal Paper No. 4938 EAS, Purdue University. 相似文献
16.
The effects of 5 μg/ml of 25-hydroxycholesterol; cholestane-3β, 5α,6β-triol; and cholesterol on acyl CoA cholesterol acyltransferase,
acid cholesteryl ester hydrolase and neutral cholesteryl ester hydrolase was studied in cultured rabbit aortic smooth muscle
cells. After 1 hour incubation, 25-hydroxycholesterol resulted in a fourfold stimulation of acyl CoA cholesterol acyltrans-ferase
activity. No stimulation by 25-hydroxycholesterol was noted before 15 minutes or after 5 hours of incubation. Neither cholestane-3β,5α,6β-triol
nor cholesterol influenced acyl CoA cholesterol acyltransferase activity at any time interval. No significant effects of any
of the sterols were noted on acid cholesteryl ester hydrolase or neutral cholesteryl ester hydrolase activity. The imbalance
between acyl CoA cholesterol acyl trans-ferase and hydrolase activities induced by 25-hydroxycholesterol could result in cholesteryl
ester accumulation by arterial smooth muscle cells, which may be associated with atherosclerosis. 相似文献
17.
Hans Stam Sietske Broekhoven-Schokker Kees Schoonderwoerd Willem C. Hülsmann 《Lipids》1987,22(2):108-115
Cholesteryl esterase activities were determined in homogenates of rat heart (ventricles), isolated, calcium-tolerant, cardiac
myocytes and aortic tissue and were compared with acid and neutral triglyceride lipase activities in these fractions.
Using cholesteryl oleate/phosphatidylcholine/taurocholate emulsions and digitonin pretreatment of the enzyme fractions, acid
and neutral cholesteryl esterase activities were measured in all tissue preparations. In contrast to the acid and neutral
triglyceridase and acid cholesteryl esterase activity, the neutral cholesteryl esterase activity was subject to substrate
inhibition. Upon isolation of cardiac myocytes, and in contrast with the recovery of neutral triglyceride lipase activity,
only a small portion of the neutral cholesteryl esterase (6%) was recovered, suggesting that nonmyocyte neutral cholesteryl
esterase activity markedly contributes to the relatively high activity detectable in whole ventricular homogenates. The recovery
of large amounts of neutral cholesteryl esterase activity in the supernatant of collagenase-digested heart tissue, obtained
during the isolation of myocytes, which is also markedly enriched in activities of two endothelial marker enzymes (5′-nucleotidase
and angiotesine-converting enzyme) may indicate the predominant contribution of neutral cholesteryl esterase activity from
coronary endothelial cells to this activity detectable in ventricular homogenates. Relative to the activity in ventricular
and myocyte homogenates, aorta homogenates possessed the highest specific neutral cholesteryl esterase activity. We propose
that in addition to coronary endothelium, smooth muscle cells also contribute to the neutral cholesteryl esterase activity
in ventricular homogenates. Pretreatment of rats with carrageenan an agent toxic to macrophages, lymphocytes and fibroblasts,
induced a significant drop in myocardial neutral cholesteryl esterase and triglyceride lipase activity, suggesting that interstitially
trapped macrophages may also contribute to lipolytic activities present in whole ventricular homogenates. Our data indicate
that caution has to be taken upon extrapolation of experimental findings in heart homogenates to myocardial muscle cells. 相似文献
18.
Cholesteryl ester hydrolase (CEH), triacylglycerol lipase (TGL) and retinyl palmitate hydrolase (RPH) were measured in 104,000
×g supernatants from rat liver under optimal conditions for measurement of cytosolic CEH. Similar levels of hydrolytic activity
were seen with oil droplet dispersions of cholesteryl oleate, trioleoylglycerol and retinyl palmitate. No cytosolic TGL activity
was seen with substrate presented in the triton-albumin emulsion used for measurement of lipoprotein lipase-like TGL associated
with hepatic plasma membrane. Cytosolic CEH, TGL and RPH were differentially partially purified by both ammonium sulfate precipitation
and anion exchange fast protein liquid chromatography (FPLC). Of the three activities, only CEH was stimulated by cholestyramine
feeding and by activators of protein kinases A and C. All three activities were inhibited by alkaline phosphatase treatment,
although to different degrees. It is concluded that these activities are catalyzed by at least three differentially regulated
enzymes with a high degree of specificity for their respective substrates. 相似文献
19.
The overall response of the rat’s cholesterol metabolism to a single ingestion of taurocholate (80 mg) was studied with the
isotopic equilibrium method. The bile acid production, measured by the daily14CO2 output of rats in isotopic equilibrium of [26-14C]-cholesterol, initially decreased and then increased. Conversely, the hepatic concentration of esterified cholesterol first
increased and then decreased. Moreover, the ingestion of taurocholate increasing the intestinal absorption coefficient of
dietary cholesterol increased the abosprtion and decreased the fecal excretion and the intestinal biosynthesis of cholesterol.
The balance of these last effects is an excess cholesterol inflow. The classical hypothesis of negative feedback regulation
of bile acid production fails to explain the observed biphasic effect of taurocholate. This compound, when its origin is exogenous,
appears to stimulate the storage of esterified cholesterol in the liver, at the expense of bile acid synthesis. This accumulation
rate takes into account not only the decrease in cholesterol transformation into bile acids but also the excess inflow of
cholesterol. As the exogenous taurocholate was eliminated from the body, cholesteryl ester hydrolysis occurred and provided
a supplementary source of free cholesterol for bile acid synthesis. 相似文献
20.
The effect of (−)N-[α-phenyl-β-(p-tolyl)ethyl] linoleamide (PTLA) on intestinal absorption of cholesterol was studied in rats.
Oral administration of 15 mg PTLA to rats resulted in a significant (P<0.05) decrease in the radioactivity in serum and liver
4 hr after administration of labeled cholesterol. The effect of PTLA was greater on the absorption of cholesteryl oleate as
compared with free cholesterol. The rate of hydrolysis of cholesteryl oleate in mucosal homogenates of rat intestine was decreased
with PTLA, suggesting that the inhibition of cholesterol absorption by PTLA is related to its effect on cholesteryl ester
hydrolysis in the intestine. 相似文献