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PubMed1977

In vivo metabolism of ceramides in rat brain. Fatty acid replacement and esterification of ceramide.

Three double-labeled ceramides, [1-14C]lignoceroyl D-erythro-[1-3H]sphingosine, [1-14C]palmitoyl D-erythro-[1-3H]sphingosine and D-[1-14C]cerebronoyl D-erythro-[3-3H]-sphingosine, were prepared and injected separately into the brains of 18-day-old rats. The animals were killed after 2 h and various sphingolipids were isolated and purified. These lipids were further fractionated into subgroups depending on their fatty acid content (nonhydroxy or alpha-hydroxy, shorter chain or longer chain), 3H/14C ratios obtained in ceramides, cerebrosides, and sphingomyelins containing different fatty acids from the injected material were much higher than the initial ratio. This observation indicates that a replacement of the fatty acid occurred in the injected ceramide. Comparison of the 3H/14C ratios of the cerebrosides and sphingomyelin in a specific fatty acid group with the ratios of the corresponding ceramide indicated that most of these lipids were derived directly from the ceramide. The 3H/14C ratio of the hydroxycerebroside obtained from cerebronyl sphingosine-injected brain was nearly twice the ratio of the injected material. In addition to these lipids, considerable radioactivity was incorporated into an unknown nonpolar material in the brains which had been injected with [1-14C]lignoceroyl or [1-14C]palmitoyl [1-3H]sphingosine. This material was tentatively identified as ceramide fatty acid ester. The 3H/14C ratio of the ester was identical to that of the injected material.

Animals↗

PubMed1976

Isolation and characterization of poly(glycosyl)ceramides (megaloglycolipids) with A, H and I blood-group activities.

Very complex glycosphingolipids with A, H and I blood-group activities were isolated from human erythrocyte membranes. The membranes were obtained from erythrocytes of blood group A, A2 and O respectively. A general formula for the antigens is: (Fuc)3-4(Gal)n(LlcNAc)n-2(Glc)1(Sphingosine)1(where Fus is fucose, Gal is galactose, GlcNAc is N-acetylglucosamine and Glc is glucose) with values of n ranging from 10-27. A-active preparations contain additionally 2-3 residues of N-acetylgalactosamine. In view of the unusual complexity of these compounds they were designated poly(glycosyl)ceramides (formerly megaloglycolipids). Individual poly(glycosyl)ceramide fractions were isolated from A erythrocytes and were found to differ by about 8 glycosyl residues per molecule forming a series of compounds with 22, 30, 38, 51 and 59 glycosyl residues per mole. Structural studies indicate that the main sequence of poly(glycosyl)ceramides consists of the residues of galactopyranose and 2-deoxy-2-acetamidoglucopyranose substituted at 3 and 4 position respectively. These residues are probably alternating. N-Acdtylglucosamine substituted at 3 position was not found in poly(glycosyl)ceramides. Brances of poly(glycosyl)ceramides originate from 3 and 6 position of galactopyranosyl residues. The number of branches is proportional to the degree of molecular complexity. In poly(glycosyl)ceramides isolated from A and A2 erythrocytes the branches are terminated with the following structures GalNAc alpha 1 leads to 3 [Fuc alpha 1 leads to 2] Gal; Fuc alpha 1 leads to 2 Gal and Gal (presumably Gal beta 1 leads to 4 GlcNAc). In poly(glycosyl)ceramides from A cells the total number of A and H-active structures per average molecule of 30-35 glycosyl residues amounts to 2.1 and 1.2 respectively while the number of terminal galactose structures is 1.8. For poly(glycosyl)ceramides from A2 erythrocytes the corresponding figures are 0.75, 3.5, and 2.1 respectively. Poly(glycosyl)ceramides from O cells comprise about 3.8 H-active structures and 1.8 terminal galactopyranosyl residues. In poly(glycosyl)ceramides with high "n" values the number of terminal galactose structures is increased. These fractions display high blood-group I activity. However, the removal of terminal galactose with beta-galactosidase affects I-activity only slightly.

ABO Blood-Group System↗

PubMed1979

Analysis and quantitation of free ceramide containing nonhydroxy and 2-hydroxy fatty acids, and phytosphingosine by high-performance liquid chromatography.

Reaction of ceramides containing nonhydroxy fatty acids with benzoyl chloride in pyridine at 70 degrees C for 1 hr resulted in N-benzoylation to form N,N-acyl,benzoyl derivatives; O-benzoylation also occurred. However with ceramides containing 2-hydroxy fatty acids and phytosphingosine only O-benzoylation occurred even on prolonged treatment. Only O-benzoylation occurred on reaction with benzoic an hydride. However, the benzoylation of ceramides with phytosphingosine could not be achieved with benzoic anhydride and this benzoylation was performed by reaction with benzoyl chloride at 70 degrees C for 4 hr. Because N,N-acyl,benzoyl derivatives of ceramides containing nonhydroxy fatty acids produced by treatment with benzoyl chloride overlap methyl benzoate on high-performance liquid chromatography, benzoic anhydride was preferable for benzoylation of ceramides with nonhydroxy and 2-hydroxy fatty acids. On the other hand, the reaction with benzoyl chloride at 70 degrees C for 4 hr was used for quantitation of benzoylated ceramides containing 2-hydroxy fatty acids and phytosphingosine. 3-(p-Phenylbenzoyl)estrone was used as an internal standard for both reactions and values for ceramides containing 2-hydroxy fatty acids obtained by the two reactions were in good agreement. This procedure was applied to measurement of the ceramide levels in the brain, liver, and kidney of rats during development. The levels of ceramides containing nonhydroxy and 2-hydroxy fatty acids in the brain, liver, and kidney increased to the adult levels and then remained unchanged. Ceramide with phytosphingosine was detected in the liver and kidney, where its concentration gradually increased with age, but it was not found in the brain. The composition of nonhydroxy fatty acids were also analyzed.

Aging↗

PubMed1979

Free ceramide, sphingomyelin, and glucosylceramide of isolated rat intestinal cells.

Free ceramide, glucosylceramide, and sphingomyelin were isolated from mature cells of adult rat small intestine. Free ceramide and ceramide cleaved from sphingomyelin by enzymatic hydrolysis were fractionated by thin-layer chromatography on borate-impregnated silica gel plates. Sphingoid bases were characterized by gas-liquid chromatography of aldehydes formed upon periodate oxidation. Fatty acids were quantified as methyl esters. Ceramide structures were confirmed by direct-inlet mass spectrometry. Free ceramide was found to contain two major long-chain bases in nearly equal quantity: sphingosine, mainly linked to palmitic acid, and 4D-hydroxysphinganine associated with C20 to C24 fatty acids, 22% being hydroxylated. Sphinganine occurred as a minor component linked to nonhydroxy fatty acids. Sphingomyelin contained the three long-chain bases and 63% of its ceramide was N-palmitoyl-sphingosine. Mass spectrometry of glucosylceramide confirmed 4D-hydroxyshingamine as the major sphingoid base associated preferentially with longer chain hydroxy fatty acids.

Animals↗

PubMed2026

Subtype-Specific Causal Effects of C16 and C24 Ceramides on Heart Failure: Evidence From Univariable and Multivariable Mendelian Randomization Analyses.

Ceramides (Cer) are bioactive lipids implicated in cardiovascular disease (CVD), yet their subtype-specific causal effects remain unclear. We performed a two-sample Mendelian randomization (MR) analysis using publicly available GWAS summary statistics to investigate the effects of C16:0-ceramide homologs (Cer16:0) and C24:1-ceramide homologs (Cer24:1) on six CVD outcomes. Instrumental variables were rigorously selected, and multiple MR methods were applied to ensure robust inference. Univariable MR identified a significant inverse association between Cer(d18:1/24:1) and heart failure (HF), which remained significant after false discovery rate correction. In contrast, the association for Cer(d17:1/16:0) did not remain significant after correction. No causal associations were observed for other CVD outcomes. When aggregating subtypes, genetically predicted higher total Cer16:0 levels were associated with increased HF risk, while no significant association was found for total Cer24:1. Multivariable MR further demonstrated that the protective effect of Cer(d18:1/24:1) on HF was robust, while estimates for C16 subtypes were attenuated and sensitive to model specification. In conclusion, our findings support a stable protective role of Cer(d18:1/24:1) in HF and highlight the complexity of subtype-specific effects among structurally related ceramides. These results underscore the importance of considering ceramide heterogeneity in cardiovascular research. Further studies are warranted to validate these findings and explore their clinical implications.

Ceramides↗

PubMed1975

Purification of G-M-1-ganglioside and ceramide lactoside beta-galactosidase from rabbit brain.

The major beta-galactosidase of rabbit brain has been purified over 400-fold. The enzyme converts G-M-1-ganglioside; Gal beta-1 yields 3 GalNAc beta-1 yields 4 (NANalpha-2 yields 3) Gal beta-1 yields 4 Glc yields ceramide (G-M-1) into Tay Sachs ganglioside GalNAc beta-1 yields 4 (NANalpha-2 yields 3) Gal beta-1 yields 4 Glc yields ceramide (G-M-2-ganglioside) and ceramide lactoside, Gal beta-1 yields 4 Glc yields ceramide (Gal-Glc-Cer) into glucocerebroside, Glc yields ceramide (Glc-Cer). The enzyme also hydrolyzes the synthetic substrates NPh-Gal and MeUmb-Gal. It is eluted as a single peak from Sephadex G-200 columns when natural and synthetic substrates were used and has an isoelectric point of 6.3. We were unable to resolve activity towards G-M-1-ganglioside and Gal-Glc-Cer by polyacrylamide electrophoresis in two buffer systems. With G-M-1 the pH optimum was 4.3 in acetate buffer and the K-m value 78 mu-M while with Gal-Glc-Cer, a pH optimum of 4.5 and a K-m of 17 mu-M were found. Hydrolysis of both natural and synthetic substrates was inhibited by gamma-D-galactonolactone, D-galactose and lactose. The data strongly suggest that a single beta-galactosidase hydrolyzes all the substrates tested.

Animals↗

PubMed1979

Factors affecting the hydrolysis of ceramide-3 by alpha-galactosidase A from human liver.

1. The effect of detergents on the catalytic properties of alpha-galactosidase from human liver was studied using p-nitrophenyl-alpha-galactoside and galactosyl-alpha(1 leads to 4)-galactosyl-beta(1 leads to 4)-glucosylceramide (ceramide-3) as substrates. 2. The hydrolysis of p-nitrophenyl-alpha-galactoside by alpha-galactosidase was inhibited by commercial preparations of sodium taurocholate and by taurocholate purified from these preparations by thin-layer chromatography. The extent of inhibition was dependent on the concentration of the detergent and on the amount of protein present. The impurities present in the preparation also inhibited the hydrolysis. 3. The inhibition of taurocholate preparations of p-nitrophenyl-alpha-galactoside hydrolysis was pH-dependent. 4. The inhibition by taurocholate of p-nitrophenyl-alpha-galactoside hydrolysis can be partly overcome by adding glycosphingolipids. 5. No significant hydrolysis of ceramide-3 occurs in the absence of detergent. Upon adding increasing concentrations of taurocholate, the rate of hydrolysis increases to a maximum value. At still higher taurocholate concentrations the activity decreases. 6. The concentrations of taurocholate giving a maximal rate of hydrolysis of ceramide-3 is dependent on the amount of protein present and independent of the ceramide-3 concentration. 7. When the pH dependence of the rate of hydrolysis of ceramide-3 was measured in the presence of a commercially available preparation of pure taurocholate or of crude taurocholate, curves with different shapes were obtained.

Ceramides↗

PubMed1979

Short chain ceramides as substrates for glucocerebroside synthetase. Differences between liver and brain enzymes.

In order to increase the sensitivity of the assay for ceramide: UDPGlc glucosyltransferase, the enzyme that makes glucocerebroside, we synthesized a variety of ceramide homologues that might be better substrates than the naturally occurring ceramides. N-Octanoyl sphingosine proved to be the best lipid tested in liver and brain. It could be added to the tissue homogenate in the dry form, as a thin layer coated on Celite, or in liposomes, prepared from lecithin and cerebroside sulfate. The liposomal form produced better replication of assay values. It is suggested that the addition of cerebroside sulfate to liposomal preparations might be a good, and more physiological, replacement for the commonly used dicetyl phosphate. A new homologue of DL-sphinganine, decasphinganine, was synthesized by an efficient series of steps and acylated with different fatty acids to form ceramide homologues. The best substrate in this series was the lauroyl amide and it is suggested that this lipid be used in cerebroside synthetase assays because of the convenience of preparing it, even though it is not as good as octanoyl sphingosine. Both compounds are distinctly better than natural ceramide or DL-sphinganine amides. From comparisons of enzyme activity under various conditions, the tentative conclusion is drawn that the enzymes in liver and brain have different properties, and that liver has two different synthetases.

Amides↗

PubMed2026

Impact of Albuminuria-Lowering Treatments on Cardiovascular Predictive Ceramides in Diabetes: Post Hoc Analysis of the ROTATE Trials.

AIM: Cardiovascular disease (CVD) is the leading cause of mortality in individuals with diabetes. Diabetic kidney disease, closely related to CVD risk, is prevalent in up to 40% of this population. Emerging evidence suggests ceramide lipids as accurate biomarkers for CVD. We assessed the effect of four albuminuria-lowering drugs on CVD-related ceramides in diabetes by post hoc analysis of the ROTATE trials. MATERIALS AND METHODS: Twenty six adults with type 1 (T1D) as well as 37 with type 2 diabetes (T2D) with a urine albumin-creatinine ratio (UACR) of 30-500 mg/g participated in a 4-week 4-time randomized crossover study with periods of telmisartan, empagliflozin, linagliptin and baricitinib treatment, each separated by a 4-week washout period. Blood samples were collected at the beginning and end of each period and ceramide lipids (Cer16, Cer18, Cer20, Cer22, Cer24 and Cer24:1) were measured. The effect of each treatment was evaluated using linear mixed-effect models. RESULTS: At baseline, individuals with T2D had greater levels of Cer22 and Cer24 compared to the individuals with T1D. Among the treatments, linagliptin was the only drug that demonstrated a reduction of Cer22, Cer24 and Cer24:1 from baseline by 22.6% (95% CI: -33.58; -9.79, p = 0.001), 25.7% (95% CI: -38.94; -9.69, p = 0.003) and 19.6% (95% CI: -31.34; -5.95, p = 0.007), respectively. No changes in the ceramides were observed for the other drugs. CONCLUSION: Our exploratory findings suggest that certain albuminuria-lowering drugs may affect ceramide levels as a secondary effect. However, further mechanistic investigations are needed.

Humans↗

PubMed1978

Properties of immobilized fig alpha-galactosidase and effect on ceramide-3 content of plasma from patients with Fabry's disease.

The possibility of lowering the level of ceramide-3 (galactosyl-alpha(1 leads to 4)-galactosyl-beta(1 leads to 4)-glucosyl-beta(1 leads to 1)-ceramide) in the plasma of patients with Fabry's disease was investigated. An immobilized alpha-galactosidase (alpha-D-galactoside galactohydrolase, EC 3.2.1.22) was prepared by coupling purified fig alpha-galactosidase to Sepharose 4B. The pH optimum for the hydrolysis of the artificial substrate p-nitro-phenyl-alpha-D-galactopyranoside was shifted by approx. 0.5--1.0 pH unit to higher pH values upon coupling of the enzyme to Sepharose 4B. The immobilized enzyme was more stable than the native enzyme to incubation at 60 degrees C. The immobilized enzyme was able to hydrolyse ceramide-3 either at pH 4.5 or at pH 7.4 in an artificial system in which sodium taurocholate was used to solubilize the substrate. In contrast, when the immobilized enzyme was incubated with normal plasma or plasma from a patient with Fabry's disease, in which elevated levels of ceramide-3 occur, no hydrolysis of the glycosphingo-lipid could be detected. The results suggest that lowering of level of ceramide-3 in plasma from patients with Fabry's disease by enzymic means is not feasible.

Drug Stability↗

PubMed1975

Surface carbohydrates of hamster fibroblasts. I. Chemical characterization of surface-labeled glycosphingolipids and aspecific ceramide tetrasaccharide for transformants.

1. Neutral glycosphingolipids of hamster fibroblast NIL cells have been characterized as follows: glucosylceramide, lactosylceramide (betaGall yields 4Glc yields Cer), a digalactosylceramide (alphaGall yields 4betaGal yields Cer), a trihexosylceramide (alphaGall yields 4betaGall yields 4Glc yields Cer), two kinds of ceramide tetrasaccharides (A: alphaGa1NAcl yields 3betaGalNAcl yields 3alphaGall yields 4betaGall yields 1Cer, a new type of Forssman active glycolipid; B: globoside, betaGalNAcl yields 3alphaGall yields 4betaGall yields 4betaGlc yields Cer), and a ceramide pentasaccharide having a classical structure for Forssman antigen (alphaGalNAcl yields 3betaGalNAcl yields 3alphaGall yields 4betaGall yields 4Glc yields Cer). 2. Neutral glycosphingolipids of polyoma virus-transformed NIL cells (NILpy) have been characterized as having an additional ceramide tetrasaccharide which was absent in normal NIL cells. The structure of this specific glycolipid was identified as lacto-N-neotetraosylceramide (betaGall yields 4betaGlc-NAcl yields 3betaGall yields 4Glc yields Cer). Chemical quantities of ceramide tetra- and pentasaccharides in NILpy cells were much lower than in NIL cells. 3. All of these glycolipids, except glucosylceramide and lactosylceramide, were labeled externally by galactose oxidase and tritiated borohydride according to the method previously described (GAHMBERG, C. G, and HAKOMORI, S. (1973) J. Biol. Chem. 248, 4311-4317). The specific activities of the label in glycolipid of NIHpy cells were much greater than that in NIL cells, i.e. reactivity of glycolipids with galactose oxidase in NIHpy cells was much higher than for NIL cells. The surface label in glycolipids was cell cycle-dependent in NIL cells, and a remarkable exposure of a galactosyl residue of a ceramide tetrasaccharide was demonstrated only on the surface of NILpy cells, due to the presence of lacto-N-neotetraosylceramide.

Animals↗

PubMed1976

Molecular arrangements in sphingolipids. Conformation and hydrogen bonding of ceramide and their implication on membrane stability and permeability.

The preferred conformation of the ceramide part of sphingolipids has been deduced from single crystal structures of a series of sphingolipid constituents: N-tetracosanoylphytosphingosine, glycosylphytosphingosine hydrochloride, sphingosine hydrochloride, triacetylsphingosine, DL-2-hydroxytetradecanoic acid and N-stearoylethanolamine. The amide group of the ceramide, which serves as a link between the hydrocarbon chains, has a basic significance for the contormation of the entire molecule. This rigid group, which comprises six atoms in a planar conformation, adopts a perpendicular orientation towards the axes of the two hydrocarbon chains. The carbonyl oxygen thereby turns into an eclipsed position with the hydrogen atoma at carbon atom 2 of the sphingosine. A parallel chain stacking is achieved by a sharp perpendicular bend of the fatty acid. This bend is produced by a sequence of two --60 degrees rotations about the C-C bonds at both sides of the alpha-carbon atom. The orientation of the hydrogen bond donors and acceptors of the amide group and the hydroxyl groups allow lateral interaction with other lipid molecules. The proposed models are supported by infrared spectra, thin-layer chromatographic behaviour and monolayer studies of synthetic model ceramides. The functional role of the hydrogen bonding groups in the ceramide part of sphingolipids is emphasized and their significance for the formation of lateral hydrogen bonds within the membrane layer and thereof arising effects on membrane stability and permeability are discussed.

Binding Sites↗

PubMed1975

Ceramidase and ceramide synthesis in human kidney and cerebellum. Description of a new alkaline ceramidase.

It has been shown that tissues of patients with Farber's disease characteristically lack acid (pH 4.0) ceramidase. In normal cerebellum, however, ceramide cleavage and the reverse reaction, free fatty acid-dependent ceramide synthesis, both occur not only at pH 4.0 but also at pH 9.0, although normal kidney exhibits these activities only at pH 4.0. Both tissues are capable of snythesizing ceramide via an acyl-COA-dependent pathway at neutral pH. The synthetic analog of ceramide, N-oleoyl-ethanolamine, is a potent inhibitor of ceramidase.

Amidohydrolases↗

PubMed1977

Studies on the glycosphingolipids of the starfish, Asterina pectinifera. I. The isolation and characterization of ceramide mono- and di-hexosides.

Ceramide mono- and di-hexosides were isolated from the starfish, Asterina pectinifera. These glycolipids had both a novel ceramide which contained almost entirely phytosphingosines (long-chain bases) and a high content of 2-hydroxy fatty acids. The long-chain base composition of the glycolipids shows an unusual pattern with both branched bases (iso-C16, iso-C17, iso-C18, anteiso-C17, and anteiso-C18) and normal ones (C16, C17, and C18). Of these, iso-C16- and anteiso-C18-phytosphingosines had been undetected up to now. The glycolipids were identified as glucosyl and lactosyl ceramides. Lactosyl ceramide had not been previously reported in starfish, although the wide occurrence of this glycolipid has been demonstrated in other organisms.

Animals↗

PubMed1978

Total synthesis of stereospecific sphingosine and ceramide.

A small-scale synthesis of the four sphingosine stereoisomers (d-erythro, l-erythro, d-threo, and l-threo) and lignoceroyl d- and l-erythro-sphingosines, which is suitable for synthesis of tritium-labeled compounds, is described. Ethyl dl-erythro-2-acetamino-3-hydroxy-4t-octadecenoate was esterified with l(+)-acetylmandeloyl chloride and the two diastereomers obtained were separated from each other by thin-layer or column chromatography. Each diastereomer was subjected to ethanolysis to obtain ethyl d- or l-erythro-2-amino-3-hydroxy-4t-octadecenoate which was then reduced with LiAlH(4) or NaBH(4) to yield d- or l-erythro-sphingosine. d-erythro-[1-(3)H]Sphingosine with high specific activity was prepared by using LiAl(3)H(4) in the last step. d- and l-threo-sphingosines were synthesized from ethyl dl-threo-2-acetamino-3-hydroxy-4t-octadecenoate by using a similar procedure. Ceramide (lignoceroyl sphingosine) was prepared either by acylating sphingosine or by the following new method. Ethyl dl-erythro-2-amino-3-hydroxy-4t-octadecenoate was converted to the N-lignoceroyl derivative and esterified with l(+)-acetylmandeloyl chloride. The two diastereomers obtained were separated and each isomer was treated with a catalytic amount of sodium ethoxide. One of the products, ethyl d-erythro-2-lignoceroylamino-3-hydroxy-4t- octadecenoate, was reduced with NaBH(4) to yield ceramide. N-palmitoyl dl-erythro-sphingosine was also prepared using an identical procedure. N-lignoceroyl d-erythro-[1-(3)H]sphingosine was prepared by NaB(3)H(4) reduction of the corresponding amide ester. A doubly labeled ceramide, [1-(14)C]lignoceroyl [1-(3)H]sphingosine, containing high specific activity, was prepared by mixing the above N-lignoceroyl d-erythro-[1-(3)H]sphingosine and N-[1-(14)C]lignoceroyl d-erythro-sphingosine. The conversion of the doubly labeled ceramide to 3-keto derivative is also described.

Carbon Radioisotopes↗

PubMed1976

Determination of the anomeric configurations of Corbicula ceramide di- and trihexoside by chromium trioxide oxidation.

The anomeric configurations of Corbicula ceramide dihexoside and ceramide trihexoside were determined by chromium trioxide oxidation and the structures of these lipids were shown to be Man-beta(1 leads to 4)-Glc-beta(1 leads to 1)-ceramide and Man-alpha(1 leads to 4)-Man-beta(1 leads to 4)-Glc-beta(1 leads to 1)-ceramide. These results are compatible with those obtained by enzymic hydrolysis reported previously.

Chromium↗

PubMed1979

Ceramide metabolism in brain.

Ceramide is the fundamental structure and key intermediate of all sphingolipids. Biosynthesis and catabolism of brain ceramide, especially their relationship to the metabolism of more complex sphingolipids in brain, are reviewed. Human genetic diseases which involve altered ceramide metabolism are also discussed.

Animals↗

PubMed1976

Rat intestinal glycolipids. II. Distribution and biosynthesis of glycolipids and ceramide in villus and crypt cells.

Intestinal epithelial cells were isolated from rat intestine and grouped into villus and crypt cell fractions. Glycolipids were purified from each cell fraction and quantitated by fluorimetric determination of glycolipid sphingosine. Significant quantities of ceramide were found in all cell fractions and accounted for approximately 15% of total glycolipid sphingosine. While villus and crypt cell fractions quantitatively contained differing amounts of sphingosine, all cell fractions contained proportionally similar quantities of sphingosine when compared to cellular cholesterol or phospholipid. Individual glycolipids, however, showed significant differences in distribution between villus and crypt cells. Hematoside and glucosylceramide were proportionally increased in villus cells, while crypt cells showed an increase in trihexosylceramide and ceramide content. The rate of UDPglucose : hydroxy fatty acid ceramide glucosyltransferase was higher in villus cells while the rate of UDPgalactose : lactosylceramide galactosyltransferase was 3--4 times increased in crypt cells. These studies demonstrate that significant differences in both the distribution and biosynthesis of individual glycolipids occur in crypt and villus cells of rat intestine and are of possible importance in the process of intestinal cell differentiation.

Animals↗