Influence of dietary cholesterol on the relative synthesis of hepatic glycerides and molecular classes of 1,2-diglycerides and phospholipids in the gerbil in vivo

The influence of dietary cholesterol on the relative rates of synthesis of hepatic lipids in the male Mongolian gerbil,Meriones unguiculatus, was studied. The semi-purified starch-based diet used lard as the dietary fat and was fed with or without a 0.5% (by wt.) cholesterol supplement. Each animal received 300 μCi [2-³H]-glycerol i.p. after 3 or 7 days on the dietary regimens. Relative rates of [2-³H]-glycerol incorporation into the major hepatic glycerides in vivo was not affected significantly by dietary cholesterol (0.5% level), suggesting that alteration in the relative biosynthesis of these lipids could not readily account for the higher triglyceride (TG) to phospholipid (PL) mass ratio in liver with cholesterol feeding. However, there was evidence for an increased formation of 1,2-diglyceride (1,2-DG). The complement of molecular species of hepatic 1,2-DG, phosphatidylcholine (PC), and phosphatidylethanolamine (PE) formed de novo, as measured using isotopic glycerol, was not influenced greatly by dietary cholesterol, although lower mean rates of synthesis of tetraenoic relative to dienoic species of phospholipids were indicated in cholesterol-fed gerbils.     

Origins of the cholesterol in milk

Studies were conducted to investigate the origin of milk cholesterol in the ruminant. In the first experiment, [1-¹⁴C] sodium acetate was infused into one side of the udder of a lactating goat via the teat canal whereas in the second, [1,2-³H] cholesterol was injected intravenously and concurrently with a [¹⁴C] acetate intrammamary infusion. In both experiments, blood and milk samples were collected at intervals for 6 days postinjection. Maximum unesterified cholesterol specific activity (sp act) in whole milk appeared at 78 hr after intravenous injections of³H cholesterol and within 3–7 hr after infusion of [¹⁴C]acetate. Virtually all the tritium in milk was associated with unesterified cholesterol. The sp act of¹⁴C-labeled cholesterol was only 20% of gland-synthesized decanoic acid. Decanoic acid is known to be completely synthesized in the mammary gland, and, like cholesterol, acetate is its precursor. The results indicate that, although some milk cholesterol is synthesized in the mammary gland, it is derived principally from serum cholesterol. The data show also that serum cholesterol equilibrates with membrane cholesterol of the lactating cell prior to its secretion in milk.     

Quantitation of 1,2-diacylglycerol in rat heart by latroscan TLC/FID

1,2-Diacylglycerol, which has been recognized as one of the intracellular second messengers, was measured quantitatively in the lipid extract from rat hearts using the thin layer chromatography and flame ionization detection (TLC/FID) method. Cholesterol acetate was added to the tissue as an internal standard, and the crude lipids from the tissue were purified with silicic acid column to eliminate phospholipids. Development of Chromarods was carried out using two solvent systems and a three-step development technique. The relationship of the peak area ratio detected by flame ionization detector to weight ratio was linear compared with cholesteryl acetate. The 1,2-diacylglycerol content in the rat heart in the unstimulated condition was 72.5±15.3 ng/mg wet wt (mean±SD).     

Glass transition temperature and chain flexibility of 1,2-polybutadiene

The solubility parameter and glass transition temperature of 1,2-polybutadiene with different 1,2-unit content have been measured. T_g increases with increasing 1,2-unit content, whereas no essential change of solubility parameter has been observed. So, it may be concluded that chain flexibility arising from internal rotation about single bond is the sole factor which determines glass transition. Chain flexibility was then studied by computation of energy of rotational isomerization ε and the steric factor ε characterizing hindrance to internal rotation. Finally, the potential barrier to internal rotation U was obtained by correlating δ and ε via T_g. The results are shown in Table VI. σ, ε and U all increase with increasing 1,2-unit content indicating rising of T_g is a result of increasing chain stiffness. Determination of the solubility parameter of 1,2-polybutadiene by viscometry with toluene–cyclohexane (similar molar volume) as mixed solvent was examined and proved to be reliable. The exponent α in the Mark–Houwink equation for 1,2-polybutadiene–toluene system was estimated from the solubility parameter of polymer and solvent according to the method of van Krevelen and Hoftzer¹⁶ and found to be 0.725. This value of α was used as a first approximation for the calculation of molecular weights from GPC data. The Mark–Houwink equations finally established for the system, 1,2-polybutadiene–toluene (30°C) with different 1,2-unit contents are given in eqs. (8)–(10).     

Effects of su-13437, a new hypolipidemic drug,upon synthesis in vivo of hepatic and carcass total fatty acids and total cholesterol

The present study is directed toward obtaining information on the metabolic effects and on the mode of action of CIBA-Su-13437, a new hypolipidemic phenolic ether structurally related to clofibrate. The ability of Su-13437 to affect the net formation of lipids in vivo was studied by measuring the total incorporation of intraperitoneally injected 1,2-¹⁴C-sodium acetate and uniformly labeled¹⁴C-glucose into total fatty acids and total cholesterol by the liver and carcass of control and Su-13437-treated mice. Treated mice received Su-13437 orally at 25, 100 or 250 mg/kg/day for 14 or 15 consecutive days. Treatment with Su-13437 resulted in pronounced enlargement of the liver and significant reductions in the plasma levels of triglycerides and total cholesterol. Essentially all of the observed metabolic effects of Su-13437 were confined to the liver. At all doses studied, in addition to liver enlargement, there were large increases in incorporation of both¹⁴C-acetate and¹⁴C-glucose carbon into hepatic total fatty acids; marked increases in hepatic total fatty acid content; and decreases in the liver’s relative cholesterol content of up to 30% with little or no effect upon the net synthesis of cholesterol per gram of liver. These observations are interpreted as indicating that Su-13437 lowers plasma triglyceride and cholesterol levels by means other than net inhibition of fatty acid and cholesterol formation by either hepatic or extrahepatic tissues.     

Dietary fat effect on incorporation and release of lipids and cholesterol by rat intestinal slices

The effect of saturated and unsaturated fats on in vitro formation and release of lipids and cholesterol from¹⁴C acetate by rat intestinal tissue was investigated. The rats were fed a basal diet enriched with either 25% corn oil or lard and then sacrificed after a 10- or 25-day feeding period. It was observed that a similar¹⁴C lipid content but a greater¹⁴C cholesterol content was found in the intestinal tissue of rats fed corn oil than in rats fed lard for 10 days. After a longer period of feeding of 25 days, the intestinal tissue¹⁴C cholesterol level was decreased in the corn oil fed rats without any significant effect on other lipids. These data suggest that corn oil in some way influences cholesterol biosynthesis depending upon its degree of unsaturation and the period of time for which it is fed. The decrease at the later time might involve some mechanism which aids in getting rid of accumulated tissue cholesterol. Less¹⁴C lipid and¹⁴C cholesterol were released by the intestinal tissue of rats fed the unsaturated fat as compared with those fed the saturated fat, suggesting a possible role in vivo in reducing blood lipids and blood cholesterol levels. Robert A. Welch Foundation.     

Upregulation of low density lipoprotein receptor activity by tumor necrosis factor,a process independent of tumor necrosis factor-induced lipid synthesis and secretion

It has been shown that tumor necrosis factor (TNF) rapidly upregulates expression of the low density lipoprotein (LDL) receptors on Hep G2 cells and acutely stimulates hepatic lipid synthesis and secretionin vivo. It may thus be possible that TNF-induced expression of LDL receptors is secondary to a decrease in cellular cholesterol content caused by TNF-stimulated lipid secretion. In order to know whether TNF upregulates LDL receptors by depletion of the cellular cholesterol content, the present experiments were designed to study the temporal relationship between TNF-stimulated expression of LDL receptor activity and TNF-induced changes in lipid synthesis and secretion in anin vitro setting by using Hep G2 cells (a highly differentiated human hepatoma cell line) as a hepatocyte model. Hep G2 cells were incubated with TNF (usually 2.5 nmol/L) for certain periods, and LDL receptor activity was evaluated by measuring [¹²⁵I]LDL binding at 4°C; lipid synthesis and secretion were assayed by measuring [³H]glycerol incorporation into triglycerides and phospholipids as well as [¹⁴C]acetate incorporation into cholesterol. We found that a 30-h exposure of the cells to TNF was needed for the effect of TNF to be seen on lipid synthesis and secretion as measured by incorporation of [³H]glycerol into triglycerides and phospholipids, whereas TNF rapidly (in several hours) upregulated LDL receptor activity. TNF stimulated triglyceride synthesis, but did not stimulate phospholipid synthesis. On the other hand, TNF stimulated phospholipid secretion, but did not stimulate triglyceride secretion. Exposure of the cells to TNF for 16 or 24 h neither decreased cholesterol synthesis nor stimulated cholesterol secretion as measured by [¹⁴C]acetate incorporation into cholesterol. Upregulation of LDL receptor activity through inhibition of cellular cholesterol synthesis with compactin (a competitive inhibitor of the 3-hydroxyl-3-methylglutaryl-CoA reductase) was augmented by TNF, whereas downregulation of LDL receptor activity through stimulation of cellular cholesterol synthesis with mevalonolactone almost completely blocked the upregulatory effect of TNF. In conclusion, TNF-stimulated expression of LDL receptor activity is not secondary to a depletion of cellular cholesterol content through TNF-stimulated lipid secretion or inhibition of cholesterol synthesis.     

Differential inhibitory effects of garlic-derived organosulfur compounds on cholesterol biosynthesis in primary rat hepatocyte cultures

Using primary rat hepatocyte cultures, the potency of several garlic-derived organosulfur compounds to inhibit cholesterol biosynthesisin toto as well as at early and late steps of this metabolic pathway was compared. Concerning early steps, allicin significantly inhibited incorporation of [¹⁴C]acetate into nonsaponifiable neutral lipids already at concentrations as low as 10 μM, while diallyl disulfide and allyl mercaptan were effective above 100 μM only. Likewise, inhibition in response to the two vinyl-dithiins started at 500 μM. If [¹⁴C]acetate was replaced by [¹⁴C]mevalonate, inhibition due to allicin, diallyl disulfide, and allyl mercaptan disappeared suggesting that HMGCoA-reductase was the target of inhibition. In contrast, for the vinyl-dithiins a stimulation of mevalonate incorporation was found. Concerning the late step, the potency to exert accumulation of lanosterol presumably by inhibiting lanosterol 14α-demethylase decreased in the order allicin>diallyl disulfide>allyl mercaptan=1,3-vinyl-dithiin≫1,2-vinyldithiin, the effect of the latter compound being close to zero. With respect to the total inhibition of [¹⁴C]acetate labeling of cholesterol, the half-maximal effective concentration-value of allicin was determined to be 17±2 μM compared to 64±7 μM for diallyl disulfide and to 450±20 μM for allyl mercaptan. Cytotoxicity as determined by the lactate dehydrogenase leakage assay was slightly higher for the two vinyl-dithiins than for diallyl disulfide and allyl mercaptan, but was apparent only at concentrations higher than 10 mM and, consequently, was irrelevant for the effects described. These results demonstrate that different garlic-derived organosulfur compounds interfere differently with cholesterol biosynthesis and, thus, may provoke multiple inhibition of this metabolic pathway in response to garlic consumption. The fact that allicin was the most effective inhibitor argues against the possibility that its degradation products, namely diallyl disulfide or allyl mercapatan, might mediate its effects, a possibility that might be true, however, in the case of the vinyl-dithiins.     

On the Quantification of Lignin Hydroxyl Groups With 31P and 13C NMR Spectroscopy

Factors affecting the accuracy of the analysis of lignin hydroxyl and carboxyl groups with ³¹P NMR have been further elucidated. Two modifications of ³¹P NMR analysis of lignin, namely the protocols using 1,3,2-dioxaphospholane (PR-I) and 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane (PR-II) as phosphorylation reagents with different internal standards, were studied. The previous ³¹P NMR standard protocol with PR-II underestimated OH groups by about 30%, whereas the ³¹P NMR standard protocol with PR-I tended to produce overestimated data. It has been shown that cholesterol is not an appropriate internal standard, resulting in underestimated values for OH groups due to incomplete baseline resolution. The best internal standard has been found to be endo-N-hydroxy-5-norbornene-2,3-dicarboximide. Strong care should be taken related to the stability of the internal standards to avoid inflated results due to IS degradation. Under modified optimized conditions, both methods show a good correlation with the ¹³C NMR protocol in the quantification of hydroxyl groups as average, with the variability between the methods in the range of 5–15%. However, the ³¹P NMR protocols report COOH content that is twice as low as that of ¹³C NMR data. Finally, the best approach for the use of the ³¹P and ¹³C NMR methods in lignin analysis is discussed.     

Dietary lipid,fatty acid oxidation and incorporation of carbon into cholesterol

Female rats (200 g) were fed a nutritionally adequate diet containing 1% by weight of corn oil (low-fat, LF), 21% of corn oil (CO) or 20% of beef tallow plus 1% of corn oil (BT) for two weeks. Food was removed for 8–12 hr, then each rat was refed for 1 hr. Each rat was injected ip with Na-³H-acetate and U-¹⁴C-Na-palmitate, (P),-oleate (O) or-linoleate (L). Expired CO₂ was collected for 2 hr. Liver, heart and serum were obtained for analysis of total lipid¹⁴C and³H and cholesterol¹⁴C and³H. Oxidation of L was twice as great as O or P when the LF diet was fed. CO and BT diets doubled oxidation of O to equal L, and increased oxidation of P, 50%. In liver and serum P was retained to a greater extent than O or L on BT and CO diets. Incorporation of acetate into total lipid was highest on LF diet and reduced by feeding either CO or BT. Incorporation of acetate into cholesterol was greater when BT or CO was fed than for LF.¹⁴C was incorporated into cholesterol in such small amounts that it was barely detectable and could not be counted accurately. Conclusions are that (a) dietary fat affects rate of oxidation of uniformly labeled palmitate and oleate, but not linoleate, (b) acetate is a more ready precursor to cholesterol than is fatty acid carbon, and (c) the acetate incorporated into cholesterol when polyunsaturated fat is fed is not derived directly from fatty acid carbon. The failure of incorporation of fatty acid carbon into cholesterol within 2 hr of administration opens the question of compartmentation of acetate as to its metabolic source. Colorado Agricultural Experiment Station Scientific Series Paper No. 1510.     

Effect of chylomicron remnants on cholesterol metabolism in cultured rabbit hepatocytes: Very low density lipoprotein and bile acid production

The interrelationship between very low density lipoprotein (VLDL) secretion and bile acid production was studied in primary culture of rabbit hepatocytes. Chylomicron remnants (CR) were added to the cultures to study their effect on VLDL secretion and bile acid production. After 24 hr preincubation of cells with CR (10–50 μg protein/mL), intercellular neutral lipid content was increased 1.5–4-fold in a dose-dependent manner. Neutral lipid accumulation was accompanied by a 70–90% reduction of [¹⁴C]acetate incorporation into cholesterol, while no stimulation of [¹⁴C]oleate incorporation into cholesteryl esters was observed. Incubation of cells with CR increased secretion of free cholesterol, triacylglycerol and apoproteins B and E in VLDL. Stimulation of VLDL cholesterol secretion was accompanied by a reduction of taurocholic acid synthesis. These data demonstrate the existence of an inverse relationship between secretion of VLDL cholesterol and bile acid production under conditions of effective uptake of triacylglycerol-rich CR by hepatocytes.     

Inhibition of cholesterol synthesis in mammary tissue,lung, and kidney following cholesterol feeding in the lactating rat

Pregnant rats were randomly allocated to one of 3 experimental dietary groups: Group 1–15.5% butter, 2% cholesterol, 0.78% sodium cholate purified diet; Group 2-standard rat diet with the addition of 10% lard and 2% cholesterol, and Group 3-standard rat diet. Plasma and milk cholesterol at 10 days postpartum were significantly elevated in dams fed exogenous cholesterol. The rat of incorporation of [1-¹⁴C] acetate into digitonin-precipitable sterols of mammary tissue slices from dams in Group 1 and Group 2 was eight-fold and two-fold, respectively, less than controls. Mammary tissue cholesterol was greater in dams fed dietary cholesterol. Thus, our data, for the first time, demonstrate that cholesterol synthesis in lactating rat mammary tissue is suppressed following cholesterol feeding. In a second experiment, the rate of incorporation of [1-¹⁴C] acetate into digitonin-precipitable sterols in kidney and lung tissue of Group 1 rats was suppressed; however, this response was not as marked as that observed in lactating mammary tissue. The concentration of cholesterol in kidney and lung was greater than controls. These results suggest that extrahepatic inhibition of cholesterol synthesis exists in the rat with a concomitant increase in tissue cholesterol.     

In Vitro hydrolysis of fungal oils: Distribution of arachidonic acid-containing triacylglycerol molecular species

Four commercially prepared arachidonic acidrich oils from the fungus Mortierella alpina were analyzed by high-performance liquid chromatography and gas chromatography. The levels of arachidonic acid and the distribution of triacylglycerol (TG) molecular species varied significantly among these oils. The major arachidonate-containing TG species were AAA, LAA, DAA, OAA, PAA, SAA, OLA, PGA, PLA, POA, and SOA where the abbreviations A, D, G, L, O, P, and S represent arachidonic (20:4n-6), dihomo-γ-linolenic (20:3n-6), γ-linolenic (18:3n-6), linoleic (18:2n-6), oleic (18:1n-9), palmitic (16:0), and stearic (18:0) acids, respectively. In vitro incubation of the TG fractions, purified from these oils with porcine pancreatic lipase for 5 min, yields a mixture of intermediate products, such as 1,2- and 2,3-diacylglycerols (1,2- and 2,3-DG), 2-monoacylglycerol (2-MG) and free fatty acids (FFA), as well as residual TG. The degrees of hydrolysis varied significantly among the four oil preparations, ranging from 35 to 57%. The levels of arachidonic acid in the residual TG and 1,2(2,3)-DG were significantly higher than those in the original TG, whereas those in the FFA fraction were significantly lower than those in 1,2(2,3)-DG and 2-MG. Results from this study suggest that the bioavailability of arachidonic acid differs among fungal oils prepared by different suppliers. These differences could be attributed to the arachidonic acid content of the oil as well as to the association of arachidonic acid with other fatty acids in the same TG molecule.     

Effects of steroids and steroid synthesis inhibitors on fecundity ofSchistosoma mansoni in vitro

In vitro egg production bySchistosoma mansoni was examined following a 72-hr incubation period in the presence of various steroids, steroid precursors, or steroid synthesis inhibitors. Mevinolin, an inhibitor of cholesterol biosynthesis, significantly decreased egg production at 10^–6 M. However, neither cholesterol (at 10^–5 M) nor any of its hydroxylated derivatives (at 10^–4 M) affectedS. mansoni fecundity. Dianisidine, an inhibitor of cholesterol metabolism to hormonal products, was also ineffective in influencing egg production. The steroid hormones progesterone, 17-hydroxyprogesterone and medroxyprogesterone acetate, all significantly decreased egg production; however, parasite muscle tension was also significantly reduced by the concentrations of these steroids needed to produce an effect on egg laying. Various androgenic hormones (androsterone, androstenedione, testosterone) and estrogenic hormones (17-estradiol and estrone) demonstrated no effect on in vitro egg production. Significant elevation in the rate of parasite oviposition was seen in the presence of the corticosteroid prednisolone (at 10^–5 M), but not by dexamethasone, a corticosteroid analog.     

Effect of tibric acid on hepatic cholesterol synthesis in rats

Male albino rats were administered various oral doses of tibric acid daily for 1 week. Serum cholesterol and triglyceride levels were reduced, but total liver content of cholesterol, phospholipids, and triglycerides was increased. Tibric acid treatment suppressed the incorporation of both [¹⁴C] acetate and [³H] mevalonate into cholesterol by liver homogenates.     

Biosynthesis of membrane cholesterol during peripheral nerve development,degeneration and regeneration

Biosynthesis of peripheral nerve cholesterol was investigated by the in vivo and in vitro incorporation of [1-¹⁴C]-acetate into sciatic endoneurium of normal rats during development, degeneration and regeneration. Labeled sterols were rapidly formed (<10 min) within the endoneurial portion of sciatic nerve after [1-¹⁴C]acetate administration by intraneural injection. The majority of labeled sterols were initially found in lanosterol and desmosterol. After six hr, the¹⁴C-labeling in both precursors was decreased to minimum, whereas cholesterol became the major labeled product of sterol. As myelination proceeded, the incorporation of [1-¹⁴C]acetate into endoneurial cholesterol decreased rapidly and reached a minimum after six no. In mature adult nerve, an increased proportion of biosynthesis of lanosterol and desmosterol also was demonstrated. The in vitro incorporation of [1-¹⁴C]acetate into cholesterol was inhibited during Wallerian degeneration. Instead, cholesteryl esters were labeled as the major sterol product. Such inhibition, however, was not observed in the adult Trembler nerve (Brain Res. 325, 21–27, 1985), which is presumed to be due to a primary metabolic disorder of Schwann cells. The cholesterol biosynthesis was gradually resumed in degenerated nerve by either regeneration of crush-injured nerve or reattachment of the transected nerve. These results suggest that cholesterol biosynthesis in peripheral nerve relies on the axon to provide necessary substrates. De novo synthesis appears to be one of the major sources of endoneurial cholesterol that forms and maintains peripheral nerve myelin. A preliminary report of this work was presented at the 17th Annual Meeting of the American Society for Neurochemistry held in Montreal, Quebec, Canada, on March 20, 1985. Part of this work was conducted while the author was associated with Mayo Clinic.     

调味品中3-氯-1,2-丙二醇的快速测定

采用同位素内标气相色谱-质谱(GC-MS)联用法,快速测定调味品中3-氯-1,2-丙二醇(3-MCPD)的含量。试样中加入3-MCPD的氘代同位素作为内标,过柱,用正己烷淋洗,乙酸乙酯洗脱,经氮吹浓缩后采用七氟丁酰咪唑(HFBI)进行衍生化,采用GC-MS选择离子监测(SIM)模式进行定性定量分析。结果表明,本方法的添加回收率≥80%;相对标准偏差≤7%;检出限达到5.0μg/kg。本方法步骤简便,溶剂用量少,定性定量准确可靠。     

Lipid biosynthesis in cultured arterial smooth muscle cells is related to their phenotype

During the atherogenic processin vivo, arterial smooth muscle cells (SMC) undergo changes in their phenotype. In the present study, rat SMC from primary cultures and from subcultures before 10 and after 200 passages, showing contractile-like, synthetic and transformed phenotypes, respectively, were compared in regard to their lipid content and biosynthesis. The rationale for comparing these phenotypes rests in the similar changes in phenotype of SMC that occur in the formation and progression of atherosclerotic lesions. Phenotype changes were shown to be associated with changes in the phospholipid content of SMC. Phospholipid levels increased, but not as significantly as did cholesterol levels when passing from contractile to synthetic and transformed cells (1.23±0.18, 2.28±0.26 and 3.25±0.23 μg/10⁶ cells, respectively). Cholesterol normalized in respect to cell protein was increased to the same extent. Lipid synthesis as judged by [¹⁴C]acetate incorporation was increased 3- to 12-fold in the synthetic and transformed cells, respectively, compared to contractile cells. After thin-layer chromatography, radioactivity was shown to be markedly increased in most of the lipid fractions, but label in the cholesterol fraction of synthetic and transformed cells was increased by 7- and 21-fold, respectively. Thus, SMCin vitro were shown to drastically increase cholesterol biosynthesis associated with phenotype changes. Such changes are known to occurin vivo and might represent a critical step in the deposition of excess cholesterol within foam cells.     

A Phytosterolemic Mixture of Sterols Inhibits Cholesterol Synthesis,Esterification, and Low-Density Lipoprotein Receptor mRNA Abundance in HepG2 Cells

HepG2 cells were incubated with a 16.5:1.7:1 ratio of cholesterol:sitosterol:campesterol (CSC), a ratio of the major sterols observed in the plasma of phytosterolemia patients, or with cholesterol alone in combination with [¹⁴C]acetate for 24 h and the radioactivity incorporated into lipids determined. Cells incubated with CSC exhibited a 40% reduction in cholesterol esterification (p < 0.05) compared to cells incubated with cholesterol alone. In addition, a 17.5-fold reduction (p < 0.05) in total cholesterol (cholesterol plus cholesteryl ester) synthesis from [¹⁴C]acetate was observed in cells incubated with CSC compared to cholesterol alone. Low-density lipoprotein receptor (LDLR) mRNA abundance was lower in cells incubated with CSC compared to cells incubated with cholesterol alone. Our results suggest that incubation of HepG2 cells with a ratio of sterols that mimic the plasma concentration seen in phytosterolemia patients reduces cholesterol esterification, total cholesterol synthesis, and inhibits LDLR mRNA abundance. We suggest that future cell and animal-based work on phytostosterolemia might employ this methodology to serve as a novel paradigm of the disease.     

The distribution of14C-labeled cholesterol in the dog: Effect of long-term epinephrine administration

A time course study of¹⁴C-cholesterol distribution in dogs was performed after the intravenous administration of 4-¹⁴C-cholesterol. Liver cholesterol attained isotopic equilibrium with plasma cholesterol within 24 hr after the administration of the labeled cholesterol. The tissue cholesterol pools of most organs attained isotopic equilibrium with plasma cholesterol between the second and ninth day after 4-¹⁴C-cholesterol had been given. Thoracic aorta cholesterol equilibrated most slowly with plasma cholesterol. Thirty-seven to 75 days after the¹⁴C-cholesterol had been given, the specific radioactivity of thoracic aorta cholesterol was 2 to 5 times greater than that of plasma cholesterol and 1.73 and 1.65 times greater than that of the abdominal and terminal aortic segments respectively. Adrenal gland cholesterol attained specific radioactivities greater than that of plasma cholesterol between the fourth and ninth day after 4-¹⁴C-cholesterol had been given, and this relationship was maintained over the 75-day period of observation. The specific radioactivity of bile cholesterol was less than that of plasma cholesterol at all time periods. The daily administration of epinephrine in oil over a period of four to seven weeks was accompanied by a more equal distribution of¹⁴C-cholesterol throughout the length of the aorta. An increase in the specific radioactivity of kidney cortex cholesterol, relative to that of plasma and kidney medullary cholesterol, also was observed in epinephrine-treated dogs.