Cholestyramine decreases apparent total tract macronutrient digestibility and alters fecal characteristics and metabolites of healthy adult dogs

Absorption of dietary lipids in the small intestine is dependent on the emulsification by bile acids (BA) and the formation of chylomicrons. Cholestyramine is a common drug used in humans-and potentially dogs-to treat BA malabsorption associated with chronic diarrhea. It is known to bind BA to form insoluble complexes, preventing their reabsorption and possibly proper emulsification and absorption of dietary fats. The objective of this study was to evaluate the effects of cholestyramine on 1) macronutrient apparent total tract digestibility (ATTD), and 2) fecal characteristics and metabolites of healthy adult dogs. We hypothesized that cholestyramine would decrease ATTD of fat and organic matter (OM), increase fecal dry matter (DM) content, and increase fecal output. Twelve healthy beagles (3.2 ± 0.8 yr; 10.4 ± 0.9 kg) were used in a randomized crossover design. All procedures were approved by the University of Illinois Institutional Animal Care and Use Committee before the study. The study included a baseline period and two 14-d experimental periods separated by a 14-d washout. All dogs were fed the same experimental diet, formulated to meet all nutrient needs recommended by AAFCO, throughout the study. Dogs were randomized into 2 groups [diet only (control) or diet + 11.4 g/d cholestyramine (8 g/d active ingredient)] in Period 1 and received the other treatment in Period 2. During the washout, all dogs were fed the diet only. Dogs were fed once daily (0800 h) to maintain BW. Total fecal output was collected during the last 4 d of each period for ATTD analysis. On day 14 of each of period, fresh fecal and blood samples were collected for metabolite analysis. Dogs fed cholestyramine had lower (P < 0.001) ATTD of DM, OM, energy, crude protein, and fat and lower (P < 0.01) fecal scores (firmer stools) than controls. Dogs fed cholestyramine had greater (P < 0.01) as-is and dry fecal output than controls. Dogs fed cholestyramine had lower (P < 0.05) fecal ammonia and phenol concentrations, but greater (P < 0.05) fecal indole, acetate, butyrate, and total short-chain fatty acid concentrations than controls. Fecal DM% and pH were greater (P < 0.01) in dogs fed cholestyramine. Our results indicate that cholestyramine, when given with a meal, is safe and well tolerated but significantly decreases nutrient digestibility and alters fecal characteristics. Future studies are required to explore the effects of cholestyramine on dogs with gastrointestinal disease.

Protic acid resin enhanced 1-butyl-3-methylimidazolium chloride pretreatment of Arundo donax Linn

To improve the cellulose digestibility of energy crop Arudo donax Linn. with cost-efficient, a novel pretreatment of protic acid resin Amberlyst 35DRY catalyzed inexpensive ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) was developed in this work. The pretreatment was performed at 160°C with [C4mim]Cl for 1.5h, followed by Amberlyst 35DRY catalyzed at 90°C for 1h. The IL-Amberlyst pretreatment was demonstrated to be effective, evidenced by the reduction in cellulose crystallinity (31.4%) and increased porosity caused by extensive swelling the undissolved biomass and partial depolymerization of the longer cellulose chain of the dissolved biomass by Amberlyst. Consequently, a higher glucose yield (92.8%) was obtained than for the single [C4mim]Cl pretreatment (42.8%) at an enzyme loading of 20 FPU/g substrate. Overall, the enhanced pretreatment was competitive by using inexpensive and recyclable IL-Amberlyst 35DRY pretreated system with shorter processing time and reduced enzyme usage.

Bile acid sequestrants: more than simple resins

PURPOSE OF REVIEW

Bile acid sequestrants (BAS) have been used for more than 50 years in the treatment of hypercholesterolemia. The last decade, bile acids are emerging as integrated regulators of metabolism via induction of various signal transduction pathways. Consequently, BAS treatment may exert unexpected side-effects. We discuss a selection of recently published studies that evaluated BAS in several metabolic diseases.

RECENT FINDINGS

Recently, an increasing body of evidence has shown that BAS in addition to ameliorating hypercholesterolemia are also effective in improving glycemic control in patients with type 2 diabetes, although the mechanism is not completely understood. Furthermore, some reports suggested using these compounds to modulate energy expenditure. Many of these effects have been related to the local effects of BAS in the intestine by directly binding bile acids in the intestine or indirectly by interfering with signaling processes.

SUMMARY

A substantial effort is being made by researchers to fully define the mechanism by which BAS improve glycemic control in type 2 diabetic patients. A new challenge will be to confirm in clinical trials the recent discoveries coming from animal experiments suggesting a role for bile acids in energy metabolism.

Stabilization effect of resin on the production of potent proteasome inhibitor NPI-0052 during submerged fermentation of Salinispora tropica

Addition of acrylic resin Amberlite XAD-7 during the fermentation of Salinispora tropica significantly enhanced the production of NPI-0052 by 69 fold. Examination of the time course of resin addition to the Salinispora tropica fermentation demonstrated that the increase in the production of NPI-052 is due to the stabilization effect by resin but not the removal of an end product feedback repression. Delay in resin addition to the fermentation led to decreases in the production of NPI-0052 to the amounts that are synthesized prior to the resin addition.

Fluvastatin Alters Platelet Aggregability in Patients With Hypercholesterolemia

BACKGROUND

Hypercholesterolemia enhances platelet aggregability. Statins have beneficial effects on cardiovascular events. The purpose of this study is to investigate whether statins inhibit platelet aggregation and, if so, the mechanisms.

METHODS AND RESULTS

Twelve patients with hypercholesterolemia were prospectively randomized in a crossover design to receive either fluvastatin (20 mg/d) or colestimide (3000 mg/d) for 12 weeks. The subjects were switched to the opposite arm for additional 12 weeks. Before and after first and second treatments, experiments were performed. Eleven age-matched volunteers with normal lipid profiles served as controls. ADP-induced platelet aggregation, platelet-derive nitric oxide (PDNO) release, intraplatelet levels of GSH and GSSG, and intraplatelet nitrotyrosine production during platelet aggregation were measured. Fluvastatin and colestimide equally lowered total and low density lipoprotein cholesterol levels in hypercholesterolemia. Platelet aggregation was greater in hypercholesterolemia than in normocholesterolemia before treatment and was altered by fluvastatin. PDNO release, intraplatelet glutathione level, and GSH/GSSG ratio were lower in hypercholesterolemia than in normocholesterolemia before treatment and were increased by fluvastatin. Intraplatelet nitrotyrosine formation was greater in hypercholesterolemia than in normocholesterolemia, and decreased by fluvastatin. Colestimide did not have such effects. In vitro application of fluvastatin dose-dependently inhibited platelet aggregation. Furthermore, in vitro application of fluvastatin dose-dependently inhibited platelet nitrotyrosine expressions and the inhibitory effects by fluvastatin were reversed by preincubation with geranylgeranylpyrophosphate.

CONCLUSIONS

Fluvastatin altered platelet aggregability in hypercholesterolemic patients in a cholesterol-lowering independent manner, which was partly mediated by the improvement of intraplatelet redox imbalance.

Cholestyramine feeding lowers number of colonic apoptotic cells in rat

Secondary bile acids that are formed in the colon by bacterial action have the potential property of eliciting pathological conditions. Apoptosis of mucosal epithelial cells is recognized as an adaptation that may counteract such pathologies. Cholestyramine, an anion exchange resin that sequesters bile salts in the gut, could decrease levels of secondary bile salt stress and thus conserve the potency of the protective action. Two groups of rats were studied: those fed 4% cholestyramine and those fed regular rat food. Rats were fed cholestyramine for 7, 14, 21, or 28 d. All animals were evaluated for cell death (apoptosis) using in situ TUNEL staining, and confirmed with single-stranded DNA (ssDNA). The effect of cholestyramine on the proliferating cell nuclear antigen (PCNA) in colonic crypt cells was also examined. Our data shows that animals fed cholestyramine for 28 d show evidence of a significant decrease in the levels of apoptotic cells in their large intestines, particularly goblet cells, when compared with the control animals and no change in cell proliferation. Thus, cholestyramine may serve as an alternative in attenuating apoptosis associated with inflammatory disorders that can result in significant enterocyte and goblet-cell death.

Effects of colestimide and/or Bofu-tsusho-san on plasma and liver lipids in mice fed a high-fat diet

Hypercholesterolemia is known to enhance the risk of coronary heart disease and fatty liver. Colestimide is an anion-exchange resin, which is not absorbed in the small intestine, decreases the intestinal reabsorption of bile acids synthesized from cholesterol in the liver and consequently increases bile acid excretion into the feces. Bofu-tsusho-san, a traditional Japanese herbal remedy, contains 18 components and has long been used as an anti-obesity agent. In the present study, we investigated the effects of colestimide and/or Bohu-tsusho-san in young male mice fed a high-fat diet. The high-fat diet supplemented with both colestimide and Bofu-tsusho-san markedly reduced the plasma levels of lipids, the liver weight and number of fatty droplets in the liver cytoplasm, and the body growth, compared with animals fed a high-fat diet alone. Neither medicine affected the blood biochemistry. Thus, the hypocholesterolemic action of colestimide, sometimes bringing light flatulence, which is improved by simultaneous administration of Bofu-tsusho-san, which activates the thermogenesis of brown adipose tissue, is suggested to reduce body mass and liver lipids, lowering the plasma levels of lipids.

Usefulness of preheparin lipoprotein lipase mass as a parameter for predicting the efficacy of colestimide

This study was conducted to clarify the characteristics of colestimide responders. Forty-seven non-diabetic patients with high levels of low-density lipoprotein cholesterol (LDL-C) received colestimide at 3,000 mg/day and were followed up for 4 months. After 4 months, body weight was reduced but the change was not statistically significant. Total serum cholesterol (TC) and LDL-C levels significantly decreased from 280 to 232 mg/dl and from 195 to 150 mg/dl, respectively (p<0.01 versus before colestimide was administered). Serum triglyceride (TG) levels increased, but the change was not significant. Preheparin lipoprotein lipase mass (preheparin LPL mass) at baseline was significantly higher in colestimide responders (greater than a 20% decrease of LDL-C: n=28) than non-responders (76.2 ng/ml versus 50.3 ng/ml, p<0.05: n=19). Next, the subjects were divided into those with a high (n=33) and low (n=14) preheparin LPL mass at baseline. LDL-C levels were significantly decreased in patients with a high preheparin LPL mass while TG levels were significantly increased in patients with a low preheparin LPL mass. These results suggest that baseline preheparin LPL mass may be a marker of the response to colestimide.

Isoenzymatic forms of human cytidine deaminase

Cytidine deaminase (CDA) purified from human placenta revealed the presence of five isoenzymatic forms that differ only in their isoelectric point. Since human cytidine deaminase exists in two variants (CDA 1 and CDA 2) with a non-conservative amino acid substitution at codon 27, in this work we demonstrate that these two variants may combine together in vitro, giving five CDA isoforms as observed in vivo from human placenta. For this purpose, each of the two forms of CDA was purified close to homogeneity and dissociated into monomers in the presence of a small amount of sodium dodecyl sulfate as a dissociating agent. The monomers were mixed together and subjected to anion-exchange chromatography and to chromatofocusing analysis in order to visualize the formation of the five isoforms. Furthermore, for both CDA 1 and CDA 2 some substrates and inhibitors of CDA were assayed, with the aim of demonstrating different kinetic behavior between the two natural variants.

Pharmacokinetics of flunixin in the cat: enterohepatic circulation and active transport mechanism in the liver

The plasma and urine pharmacokinetics of flunixin-meglumine (FNX) in cats were examined using a total of 12 adult animals. After an intravenous injection of FNX (2 mg/kg), the plasma concentration time curves showed a profile of a two-compartment open model with an elimination half-life of 6.6 h. In spite of high plasma protein binding (>99%), the V(d)beta was unusually large, 0.7 L/kg. Although the recovery of FNX from urine was only 0.4% of the dose, the estimated inherent renal clearance closely corresponded to the renal plasma flow rate, indicating that a renal active tubular secretion was involved in the pharmacokinetics of FNX. Cholestyramine (ChSA), an anion exchanger, was orally administered immediately before the FNX injection in order to determine the involvement of enterohepatic circulation in FNX pharmacokinetics. The elimination phase of the profile of FNX was prevented by the concomitant administration of ChSA, so it was concluded that the drug undergoes enterohepatic circulation in cats. Pravastatin (PV) is a specific substrate of the type-2 organic anion transporting polypeptide transporter (OATP-2) in human liver cells. The effect of a concomitant intravenous injection of PV with FNX was examined in order to determine the involvement of OATP-2 like transporter in the pharmacokinetics. The V1 and total body clearance were decreased after the injection of PV. In conclusion, at least two active transport mechanisms are involved in the pharmacokinetics of FNX in cats. One pathway is renal tubular secretion and the other is sinusoidal active uptake by liver cells. The latter may be responsible for the enterohepatic circulation of FNX in cats.

Inhibition of ileal bile acid absorption by colestimide

BACKGROUND

Colestimide is a new type of anion-exchange resin in Japan, but its effect on bile acid absorption in the ileum has not been studied.

METHODS

Absorption of ursodeoxycholate, tauroursodeoxycholate, cholate, taurocholate and taurolithocholate-sulfate in rat ileum was compared in the presence and absence of colestimide. Bile acid adsorption by colestimide in vitro was also studied.

RESULTS

All bile acids were efficiently absorbed by the ileum, and the cumulative absorption during 60 min was 25-78%. The absorption of ursodeoxycholate, tauroursodeoxycholate and taurocholate was inhibited by colestimide, whereas that of cholate and taurolithocholate-sulfate was not inhibited by colestimide. Adsorption of bile acids by colestimide in vitro was higher with taurine conjugates than with the unconjugated forms.

CONCLUSIONS

Colestimide was shown to be useful to inhibit the physiologically important ileal absorption of bile acid amides in vivo.

Purification and characterization of the deoxynucleoside monophosphate kinase of bacteriophage T5

Deoxynucleoside monophosphate kinase (dNMP kinase) of bacteriophage T5 (EC 2.7.4.13) was purified to apparent homogeneity from phage-infected Escherichia coli cells. Electrophoresis in sodium dodecyl sulfate-polyacrylamide gel showed that the enzyme has a molecular mass of about 29 kDa. The molecular mass of dNMP kinase estimated by analytical equilibrium ultracentrifugation turned out to be 29.14 +/- 3.03 kDa. These data suggest that the enzyme exists in solution as a monomer. The isoelectric point of dNMP kinase was found to be 4.2. The N-terminal amino acid sequence, comprising 21 amino acids, was determined to be VLVGLHGEAGSGKDGVAKLII. A comparison of this amino acid sequence and those of known enzymes with a similar function suggests the presence of a nucleotide-binding site in the sequenced region.

Effect of colestimide on absorption of unconjugated bile acids in the rat jejunum

BACKGROUND

Colestimide is a newly developed bile acid-binding resin in Japan, but its bile acid-binding properties have not been studied.

METHODS

The absorption of unconjugated bile acids (5 mmol/L) in the ligated rat jejunum was compared in the presence and absence of colestimide. Furthermore, bile acid adsorption by colestimide was also studied in vitro.

RESULTS

All bile acids were efficiently absorbed in the jejunum and the cumulative absorption during 120 min was 29-63%. The absorption of chenodeoxycholate, lithocholate, deoxycholate and ursodeoxycholate was dose-dependently inhibited by 2.5 and 5 mg colestimide, whereas the absorption of cholate was not inhibited, even in the presence of 5 mg colestimide. Adsorption of bile acids by colestimide in vitro was approximately 60% for chenodeoxycholate, lithocholate, deoxycholate and ursodeoxycholate, whereas the adsorption of cholate was low (16%).

CONCLUSIONS

Jejunal absorption of ursodeoxycholate was inhibited by colestimide to a similar extent as other dihydroxy bile acids, whereas that of cholate was not inhibited under the same conditions.

Effect of colestimide on intestinal absorption of ursodeoxycholic acid in men

Colestimide is a new anion-exchange resin which is used to lower serum cholesterol levels in Japan. Because of its excellent compliance, colestimide can replace cholestyramine in the treatment of pruritus. However, there may be an interaction in cholestatic patients undergoing treatment with ursodeoxycholic acid (UDCA). Therefore, we studied the effect of colestimide on the absorption of UDCA in men. Five healthy men took two 100 mg tablets of UDCA after a test meal following an overnight fast, and blood samples were collected every 30 min for 3 h. Two weeks later, the same study was repeated just after taking colestimide granules (1.5 g). Bile acid subfractions in serum were measured by HPLC. Serum UDCA levels after 30 min (mainly unconjugated), which reflect the initial absorption, were decreased > 50% by colestimide in 4 out of 5 subjects. Serum total bile acid levels after 30 min, which reflect the initial absorption of bile acids due to postprandial bile secretion, were decreased by colestimide in all subjects. These results indicate that colestimide administration before the meal inhibits UDCA absorption.

In vitro assessment of the mucoadhesion of cholestyramine to porcine and human gastric mucosa

Previous in vivo studies have suggested that the extended gastric residence and uniform intragastric distribution of cholestyramine may be due to mucoadherent properties. This series of in vitro investigations explored the possibility of the anion exchange resin exhibiting bioadhesive behaviour, and investigated the characteristics, such as particle size and surface charge, that may affect it. Tensile strength measurements were carried out to determine the mucoadhesion of cholestyramine and other test materials (resin particulates, polymers and hydrogels) with varying adhesive properties, to isolated porcine and human gastric mucosa. Optimal instrumental parameters for the system were determined initially and used; all procedures were carried out at room temperature (22 degrees C). The particle size of cholestyramine did not affect mucoadhesion to either porcine or human gastric mucosa (P=0.673, porcine; P=0.969, human), whilst anionic exchangers were found to provide better mucoadhesion than cationic exchangers (P=0.0002, porcine; P=0.0009, human). In some instances, it was found that the detachment forces recorded were lower with human gastric mucosa than with porcine gastric mucosa, although this was not consistently statistically significant. A rank order of mucoadhesion was constructed from a comparison of cholestyramine with eight other test materials. Cholestyramine produced the second highest degree of mucoadhesion, with Carbopol producing the greatest adhesion. Dextran and polyethylene glycol did not display good mucoadhesion under these conditions. From the findings presented here, we have found that cholestyramine demonstrates good mucoadhesion to both porcine and human gastric mucosa when compared to other known bioadhesives. It is suggested that particle size does not contribute to this mucoadherent behaviour but the surface charge of the resin has a significant part to play.

Dietary cholestyramine reduces ochratoxin A-induced nephrotoxicity in the rat by decreasing plasma levels and enhancing fecal excretion of the toxin

Ochratoxin A (OTA) is a mycotoxin that may contaminate animal feed (oat, barley, and rye) and food (wheat, rice, coffee, beer, pig meat), leading to major health problems (e.g., nephropathy) in several animal species including humans. Several methods have been tested to reduce the toxicity of OTA in animals but with limited success. In rats, the effect of cholestyramine (CHA), a bile acid-binding resin, was investigated on OTA-induced nephrotoxicity and bioavailability. Animals were fed semisynthetic diets containing two levels of OTA: 1 or 3 ppm. At each level of OTA, the diets were enriched with 0.1, 1, and 5% of CHA. The results showed that CHA decreased the concentration of OTA in plasma. At 1 and 3 ppm of OTA in the diet, CHA is effective at a level of 0.1% and 5%, respectively. The excretion of OTA and its metabolites (ochratoxin alpha and hydroxylated ochratoxin A) in bile and urine was also decreased by addition of 5% CHA in the diet. This was associated with an increase of OTA excretion in feces. Enzymuria and renal morphology revealed that dietary CHA can decrease OTA-induced nephrotoxicity, probably by reducing renal exposure to the toxin. In conclusion, CHA can reduce OTA concentrations in plasma as well as reducing nephrotoxicity, which may be attributed to a decrease of bioavailability and/or enterohepatic circulation of the toxin.

Antitumor effect of positively charged resin in the hamster cheek pouch model

Following the signal observation that contact with positively charged dextran resin (PCDR) inhibited the growth of cultured mammary (Hs578T and MDA-MB-231), pancreatic (H2T), and myeloma (RR-658) tumor cell lines, studies were developed in the hamster cheek pouch model using hamster H2T pancreatic tumor cells to determine if the antiproliferative effect of PCDR could inhibit tumorigenesis. In these studies, the control population represented groups injected with H2T cells alone or in combination with either neutral or negatively charged resin. When cells (5 x 10(2) to 1 x 10(5)) and PCDR were administered simultaneously, the tumor incidence (percent engraftment) and growth of tumors that already had been established were significantly reduced. When PCDR was injected into already established 1-35-mm2 H2T tumors (engraftment for 21 days = 96%), the resin suppressed the growth of the smallest tumors (< 10 mm2). In none of these trials was the somatic growth of the host hamsters affected. PCDR contact with H2T cells in vitro for 4 days or used to treat growing solid tumors for 72 days significantly reduced cellular ornithine decarboxylase activity. While the mechanism of PCDR action has not been established, the observations have implications for in vivo tumor therapeutic models.

Effect of microgravity on Escherichia coli and MS-2 bacteriophage disinfection by iodinated resins

Experiments on chemical disinfection by iodinated resins were conducted on STS 50 (USML-1), which flew a 13 day mission during 1992. Fluid processing apparatus containing microorganisms and iodinated resins was assembled in either Manhattan, Kansas, or Boulder, Colorado, and loaded on-board the Space Shuttle for the mission. Pentaiodide resin was more effective than the triiodide resin against Escherichia coli. Both resins were more effective bactericides at unit gravity than microgravity because of cosedimentation of bacteria and iodinated resin beads. In bacteriophage experiments, the triiodide resin reduced the viable titer of MS-2 by nine logs. The few viable phage surviving chemical disinfection were associated with precipitant formation in the fluid processing apparatus.

Effects of cholestyramine and parenteral nutrition on hepatic metabolism of lidocaine: a study using isolated rat liver perfusion

BACKGROUND

The effect of an oral bile salt binder, cholestyramine, on parenteral nutrition-related hepatic dysfunction and lidocaine metabolism was studied in rats.

METHODS

Rats were randomly assigned to one of three treatment groups: the PN group received infusions of dextrose and amino acids; the PNC group was treated the same as the PN group, but also received oral cholestyramine; CF group animals were fed rat food and water. Lidocaine metabolism was studied in livers isolated from animals after 7 days of parenteral nutrition.

RESULTS

No differences in liver function test values of PN and PNC groups were detected compared with group fed rat food. However, lidocaine metabolism was found to be significantly reduced in both the PN and PNC groups. Significant reductions were observed in the hepatic extraction ratio (23% and 15%) and in intrinsic clearance (61% and 53%) in PN and PNC animals, respectively (p < .05). Material balance at steady state showed that recovery of lidocaine was threefold higher in the PN group and twofold higher in the PNC group than the rat food group (p < .05). Metabolite-to-drug ratios were determined for each lidocaine metabolite and this revealed significant reductions in N-dealkylation (64% and 57%) and aryl methyl hydroxylation (92% and 86%) in PN and PNC animals, respectively (p < .05).

CONCLUSIONS

Histologic findings suggest that cholestyramine feeding prevented liver dysfunction, possibly through interruption of secondary bile salt reabsorption. However, lidocaine metabolism was still impaired after cholestyramine ingestion; the impairment mechanism remains unknown.

Effect of cholestyramine resin on single dose valproate pharmacokinetics

Cholestyramine, a nonabsorbable anion exchange resin, has been reported to bind concomitantly administered drugs and decrease their bioavailability. The objective of the study was to determine the effect of cholestyramine on the plasma concentrations of valproic acid (VPA) following concurrent and staggered (VPA 3 hours before cholestyramine) dosing. Six healthy volunteers participated in an open-label, 3-way crossover study. In each phase fasting subjects received 250 mg of VPA followed by serial blood sampling for VPA plasma concentrations over a 37-hour period. In the concurrent and staggered phase the subjects received 4 g of cholestyramine (CHOL) twice daily 24 hours prior to and following the VPA dose. During the concurrent phase the coadministration of CHOL resulted in a decrease (p < 0.05) in the area under the curve (AUC) for VPA compared to VPA alone (415.2 +/- 113.2 mg*hr/l vs 489.2 +/- 153.0 mg*hr/l, respectively). When the same dose of each drug was administered 3 hours apart, the AUC for VPA (454.8 +/- 123.1 mg*hr/l) was not significantly decreased when compared to VPA alone (489.2 +/- 153.0 mg*hr/l). Also, the bioavailability relative to VPA alone was 86.2% +/- 7.1 for the concurrent phase and 95.3% +/- 13.6 for the staggered phase. Based on the AUC of VPA concurrent administration of CHOL significantly decreases VPA absorption and separating the doses of the 2 drugs by 3 hours may lessen the interaction.

Purification and characterization of prostaglandin-H E-isomerase, a sigma-class glutathione S-transferase, from Ascaridia galli

Comparison of partial primary sequences of sigma-class glutathione S-transferases (GSH) of parasitic helminths and a GSH-dependent prostaglandin (PG)-H D-isomerase of rat immune accessory cells suggested that some of the helminth enzymes may also be involved in PG biosynthesis [Meyer and Thomas (1995) Biochem. J. 311, 739-742]. A soluble GSH transferase of the parasitic nematode Ascaridia galli has now been purified which shows high activity and specificity in the GSH-dependent isomerization of PGH to PGE, comparable to that of the rat spleen enzyme in its isomerization of PGH to PGD, and similarly stimulates the activity of prostaglandin H synthase. The enzyme subunit is structurally related to the rat spleen enzyme and sigma-class GSH transferases of helminths according to the partial primary sequence. The data support the hypothesis that some sigma-class GSH transferases of helminth parasites are involved in PG biosynthesis which, in the case of PGE, is likely to be associated with the subversion or suppression of host immunity. A PG-H E-isomerase of comparable specificity and activity has not previously been isolated.

Effect of DMPS and various adsorbents on the arsenic excretion in guinea-pigs after injection with As2O3

The present experiments were performed to test the possibility of interrupting the enterohepatic circulation of arsenic (As). Therefore the efficacy of adsorbents to bind As and/or As-DMPS adducts in vitro and their effect on the excretion of As into the feces and urine in vivo were investigated after injection of As2O3 and DMPS in guinea-pigs. The adsorbents bentonite, activated charcoal or colestyramine, respectively, were tested. Only slight binding of 73As (< 5% of the 73As dose) was observed to all adsorbents in vitro. After addition of DMPS, a good binding was found for 73As to colestyramine (50%) or activated charcoal (60%), respectively. However, the 73As-DMPS adduct was removed from the activated charcoal during washing. In the first in vivo experiment, male guinea-pigs (n = 4/group) received As2O3 [0.02 mmol As(III)/kg s.c. labelled with a tracer dose of 73As(III) (0.14 kBq/g)], 30 min later DMPS (0.1 mmol/kg i.p.) and by gastric tube (10 ml/kg body wt) either saline, bentonite (1 g/kg), activated charcoal (1 g/kg) or colestyramine (0.2 g/kg), respectively. Urine and feces were collected for 24 h. No increase in 73As excretion into the feces was observed after administration of DMPS and all adsorbents, compared to control animals. In the second in vivo experiment male guinea-pigs (n = 4/group) received the same As2O3 (+ 73As)- and DMPS dose. In addition, with a gastric tube (10 ml/kg) saline, colestyramine (0.2 g/kg), DMPS (0.1 mmol/kg), or the combination of DMPS (0.1 mmol/kg) + colestyramine (0.2 g/kg) were administered according to the scheme given in the following table. The amount of feces excreted did not differ between groups. Excretion of 73As within the feces during the first 12 h after As injection is shown in the following table (mean +/- SEM). The same amount of 73As (34% of the 73As dose) was excreted into the urine from animals in groups 4 and 5 during this time. Obviously, the combined oral administration of DMPS + colestyramine markedly enhanced fecal excretion of As mobilized by DMPS i.p. It is suggested that interruption of enterohepatic circulation of As may be a valuable adjunct in the treatment of As poisoning.

Enhanced fecal excretion of bile acids by a new anion-exchange resin possessing a spacer arm in rats

The effect of a new polystyrene-based, strongly basic, anion-exchange resin possessing an omega-oxobutyl chain as a spacer arm on the fecal bile acid excretion was investigated in rats and compared with that of Dowex 1-X2, chemically equivalent to cholestyramine. The new resin did produce a significant rise in the total fecal bile acid excretion with its ingestion for a period of 4 weeks. Its promoting activity proved to be 2.0- and 1.8-fold more potent than that of Dowex 1-X2 at the 3rd and 4th week, respectively. These results suggest that the introduction of a spacer arm between the polymer backbone and a functional group would lead to an improvement in the in vivo adsorptive efficiency of the resin.

Mechanism of action of bile acid sequestrants and other lipid-lowering drugs

Although the primary and direct action of the bile acid sequestrants is to bind bile acids in the gut, their interruption of the enterohepatic recirculation of bile acids has important effects on hepatic lipoprotein metabolism. Three key enzyme systems are affected: phosphatidic acid phosphatase, cholesterol 7 alpha-hydroxylase, and 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase. Activation of phosphatidic acid phosphatase promotes hepatic triglyceride (TG) synthesis, induces secretion of TG-rich, very low density lipoprotein particles, and consequently, increases plasma TG levels. The activation of hepatic cholesterol 7 alpha-hydroxylase promotes the conversion of intracellular cholesterol to bile acids. The decrease in intracellular cholesterol stores, in turn, increases low-density lipoprotein (LDL) receptor expression on hepatocyte surface membranes and, consequently, receptor-mediated fractional catabolism of LDL. Reduction of intracellular cholesterol may also increase the synthesis of cholesterol through activation of HMG CoA reductase. The potential loss of the sequestrant's cholesterol-lowering efficacy can be overcome by adding a drug to the regimen that inhibits HMG CoA reductase. Finally, bile acid sequestrants promote apoprotein AI synthesis by an unknown mechanism and tend to raise high-density lipoprotein (HDL) cholesterol levels, primarily by increasing plasma HDL-2 concentrations.

Effects of resins and activated charcoal on the absorption of digoxin, carbamazepine and frusemide

1. The interference of resins and activated charcoal with the absorption of digoxin, carbamazepine and frusemide was studied. 2. In a cross-over study consisting of four phases, single doses of colestipol hydrochloride (10 g), cholestyramine (8 g), activated charcoal (8 g) or water only were given to six healthy volunteers immediately after the simultaneous ingestion of digoxin (0.25 mg), carbamazepine (400 mg) and frusemide (40 mg). Plasma and urine concentrations of the test drugs and the urine volumes were determined up to 72 h. 3. The absorption of digoxin was not reduced by colestipol, moderately (30-40%, P less than 0.05) reduced by cholestyramine and greatly (96%) by charcoal. 4. The absorption of carbamazepine was not decreased by cholestyramine, slightly (10%) by colestipol and greatly (90%) by activated charcoal. 5. The absorption and the diuretic effect of frusemide were significantly diminished by all agents. The bioavailability was reduced by colestipol 80%, by cholestyramine 95% and by activated charcoal 99.5%. 6. The interference with the gastrointestinal absorption of most of the basic drugs by colestipol and cholestyramine seems to be minimal. On the other hand, the resins may seriously impair the absorption of certain acidic drugs, for example frusemide.

Escherichia coli adherence to anion exchange resin. In vitro model for initial screening of potential antiadherence agents

The first step in developing a bladder infection is attachment of bacteria to the bladder epithelium. Removing the bladder mucin increases bacterial adherence up to a thousand-fold, and this increase can be prevented by pretreating the mucin-deficient bladder with heparin. To develop a rapid, in vitro antiadherence screening assay, we studied the adherence of Escherichia coli to various chromatography resins and the ability of heparin and other agents to antagonize this attachment. The results can be summarized as follows: Although E. coli attached to all resins, only the adherence to the anion exchange resin was inhibited by heparin (up to 95%). Agents which did not effect E. coli adherence to the resin did not affect attachment to the bladder. Agents which inhibited E. coli adherence to the bladder also inhibited E. coli adherence to the resin. Similar to the effect of heparin on E. coli attachment, the adherence of Klebsiella ozaene, Proteus mirabilis, and Streptococcus fecalis to both bladder epithelium and anion exchange resin were also antagonized. These studies indicate that the adherence of E. coli (as well as other bacterial species) to anion exchange resin responds to heparin and other chemical agents in a similar manner as does adherence to the mucin-deficient rabbit urinary bladder. Because of the ease and rapid nature of this in vitro assay, it serves as a useful screen for potential bacterial antiadherence agents and could be used to help elucidate mechanisms of bacterial attachment.

An evaluation of MES (2(N-Morpholino)ethanesulfonic acid) and Amberlite IRC-50 as pH buffers for nutrient solution studies

All buffering agents used to stabilize pH in hydroponic research have disadvantages. Inorganic buffers are absorbed and may become phytotoxic. Solid carbonate salts temporarily mitigate decreasing pH but provide almost no protection against increasing pH, and they alter nutrient absorption. Exchange resins are more effective, but we find that they remove magnesium and manganese from solution. We have tested 2(N-Morpholino)ethanesulfonic acid (MES) as a buffering agent at concentrations of 1 and 10 mol m-3 (1 and 10 mM) with beans, corn, lettuce, tomatoes, and wheat. MES appears to be biologically inert and does not interact significantly with other solution ions. Relative growth rates among controls and MES treatments were nearly identical for each species during the trial period. The pH was stabilized by 1 mol m-3 MES. This buffer warrants further consideration in nutrient research.

Effect of diet on T-2 toxicosis

T-2 toxin is an emetic trichothecene mycotoxin produced by Fusarium molds. This compound causes feed refusal, emesis and lesions in the gastrointestinal tract of livestock, poultry and man. Studies in our laboratory have indicated that the feeding of high fibre diets, non-nutritive mineral additives and high fat diets can largely overcome feed refusal caused when T-2 toxin is fed to rats. Subsequent experiments were designed to determine the mechanism by which such diets exert this effect. Rats were fed for two weeks diets containing varying levels of alfalfa meal, bentonite or corn oil in a casein-based semi-purified diet. Rats were then orally dosed with [3H] T-2 toxin and urine and feces were collected for 21 hours after which all animals were killed and tissues excised. Diet had no significant effect on the fraction dose of 3H excreted in the urine. Significant increases in fecal excretion of 3H were seen, however, with all test diets. Only high fat diets reduced hepatic residues of 3H while alfalfa had a similar effect in kidney and both alfalfa and bentonite lowered muscle residues. It was concluded that such dietary treatments overcome T-2 toxicosis mainly by promoting fecal excretion of toxin thereby reducing absorption and biological half-life.

Role of bentonite in prevention of T-2 toxicosis in rats

Experiments were conducted to determine the effect of bentonite and nonnutritive dietary polymers on toxicity and metabolism of T-2 toxin in rats. Male weanling rats were fed diets containing 5% bentonite, anion exchange resin, cation exchange resin or vermiculite-hydrobiotite. Each diet was fed with and without 3 micrograms T-2 toxin/g of feed for 2 wk. Bentonite and anion exchange resin were the treatments most successful at overcoming growth depression and feed refusal caused by T-2 toxin. Subsequent experiments tested bentonite and anion exchange resin at 0, 2.5, 5.0, 7.5 and 10% of the diet. Bentonite fed at 10% was the most effective treatment at overcoming feed refusal and growth depression. Rats were fed 0, 5, 7.5 or 10% bentonite for 2 wk and then dosed with [3H] T-2 toxin. Urine and feces were collected for 21 h after dosing and tissues were excised for determination of residual 3H. Feeding bentonite had little effect on the fraction of the dose excreted in the urine. Significant increases in fecal excretion of 3H were shown, when the feeding of 5, 7.5 or 10% bentonite was compared with the casein-based, semi-purified control diet. Dietary bentonite had no effect on residual 3H in liver or kidney, but all concentrations of bentonite tested reduced residual 3H in muscle. More 3H was found in the digesta in the small intestine and in the wall of the intestinal tissue when rats fed 5% bentonite were compared with the controls. Intestinal transit time for rats fed bentonite diets was reduced compared with that of the controls as indicated by chromic oxide marker studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of resin disinfectants-I3 and -I5 on Giardia muris and Giardia lamblia

The resin-I5 column developed in our laboratories rendered aqueous suspensions containing up to 5 X 10(4) cysts of Giardia muris or Giardia lamblia per ml incapable of excystation. The inhibition of excystation was effective at both 4 and 25 degrees C. The addition of Na2S2O3 to column eluates containing cysts appeared to partially reverse the disinfectant action, and the reversal was more pronounced at 4 degrees C than at 25 degrees C. In contrast, the rapid removal of cysts from the column eluates by centrifugation and filtration or the use of other reductants, notably cysteine and glutathione, did not similarly reverse the disinfectant properties of the column. Based on these data, we suggest that the disinfecting agent is acquired by the cyst in its passage through the resin column and that either the disinfecting agent or its reaction can be partially and specifically neutralized by Na2S2O3. We hypothesize that the time between disinfectant acquisition and activity is a function of the thickness of the Giardia cyst wall and consequently takes longer at the lower temperature. Nevertheless, resin-I5 appears to inactivate a larger number of cysts in a shorter period of time with lower residual halogen levels than do agents of other published methods.

Cation exchange--a common mechanism in the storage and release of biogenic amines stored in granules (vesicles)? I. Comparative studies on the uptake of sodium and biogenic amines by the weak cation (carboxyl) exchangers Amberlite IRC-50 and Sephadex C-50 and by biogenic (granule-enriched) materials in vitro

Studies on the uptake and storage of sodium and biogenic amines (phenylethylamine, noradrenaline, histamine) by two weak cation-exchangers, IRC-50 and Sephadex C-50, and by biogenic granule-enriched preparations demonstrated that the synthetic and biogenic materials had several common characteristics. They showed similar concentration- and pH-dependence and fitted the same cation-exchange and receptor-binding equations. The observations were taken to support the view that the matrices of amine-storing granules have the properties of weak cation-exchangers, with carboxyls as the cation-binding groups.

Dietary influences on excretory pathways and tissue residues of zearalenone and zearalenols in the rat

Experiments were conducted with male weanling rats to determine the effect of high dietary protein (40% casein), alfalfa (25%), protein + alfalfa (25% casein + 25% alfalfa), or anion-exchange resin (5%) on the relative proportions of free and conjugated zearalenone and zearalenols excreted in urine and feces following a single oral dose of zearalenone. About 90% of the dose was excreted in feces after 48 h while the remaining 10% was excreted in urine. Zearalenone and metabolites were excreted mainly in free form with conjugates being found only in urine. Rats fed high-protein diets excreted more free zearalenone and alpha-zearalenol in urine than did controls (16.3% casein). The feeding of protein + alfalfa also resulted in increased urinary losses of free zearalenone. A reduction in urinary losses of conjugated zearalenone and alpha-zearalenol was seen when 5% anion-exchange resin was fed. Fecal excretion of zearalenone and alpha- and beta-zearalenol increased when alfalfa + protein was fed. Residual zearalenone and zearalenols were measured in liver and kidney 18 h after dosing. All treatments except high protein reduced residues of zearalenone and alpha-zearalenol in liver when compared with controls. Renal residues of zearalenone were lowered only by supplements of protein + alfalfa or anion-exchange resin. Each of the treatments fed has been shown to reduce zearalenone toxicosis in rats, but it was concluded that each does so by a different mechanism.

Reduction of exogenous oxalate in urine of rats by binding with aluminium-oxyhydrate (Andursil) and an anion-exchanger (Colestid) in the intestinal tract

The influence of calcium carbonate, aluminium oxyhydrate (Andursil) and an anion exchanger (Colestid) on the absorption of oxalate from the intestine in rats was investigated. The animals were administered daily doses of 15mg oxalate as a 14C-sodium-oxalate solution by means of a throat probe, and the substances of interest were mixed with the food. The intake of food and the 14C-activity in the urine were measured during four urine-collecting periods of 3 days each. The quantity of the enterally administered oxalate excreted with urine has a negative correlation to the amount of the investigated test substances ingested with food.

[Effect of FAF anionite swelling on its sorption properties]

Experiments were carried out to clarify the effect of swelling coefficients of various samples of the polycondensation anion exchange resin FAF in the C1 form on its sorption properties. The anion exchange resin was used to eliminate contaminating proteins and low molecular weight agents from the allantois fluid and liver cultured cells of pigs. Thermal treatment of the anion exchange resin increased the coefficient of its swelling, leaving the structure unchanged. The resin structure was controlled by electron microscopy and X-ray scattering of low angle. When the resin samples with the swelling coefficients of 3.5 and 4.0 were used, 30-40% of proteins, 50% of reducing agents and neutral carbohydrates and a small quantity of phosphorus were adsorbed.

[Cultivation of Bordetella pertussis in liquid semisynthetic nutrient media with ion-exchange resins]

The possibility of optimizing the processes of B. pertussis cultivation carried out in liquid semisynthetic culture media with strong-base anion-exchange resins is shown. The use of strong-base ionites enhances the reproducibility of cultivation processes, increases the activity of microbial populations and the concentration of microorganisms. B. pertussis cultures grown in the media with anion-exchange resins are characterized by pronounced biological activity.

[Isolation and purification of urokinase]

An improved procedure is developed for isolation of urokinase from human urine by means of ion exchange on cyrboxyl cationite SMT at pH 4.7. with subsequent stepwice elution by phosphate buffer, rH7.0. Depigmentation of the urine was achieved by pretreatment with an anionite FAF. Chromatographically pure preparation of urokinase was obtained as shown by gel filtration through Sephadex G-100 and G-150.

[Test of efficacy of an oxalate-binding anion exchanger Colestid in healthy subjects for use in idiopathic calcium-oxalate urolithiasis]

Sodium oxalate (402 mg) was administered in a single dose to 10 healthy volunteers receiving a controlled diet. Half the group received 3 times 10 g Colestid and the other half 4 times 2 g Andursil. On the 5th day the oxalate load was repeated. Urine was collected within 32 hours following oxalate application in 8 fractions. In each fraction the levels of oxalate, calcium, phosphate and uric acid were determined. The amount of oxalate, phosphate and uric acid measured in the group receiving Colestid was lower in all fractions. Peak excretions of oxalate found in unmedicated volunteers were suppressed following oxalate load. In the group receiving Andursil, only the excretion of phosphate was decreased. The results presented suggest that Colestid may be promising in the prevention of calcium-oxalate-urolithiasis.

Effect of bile salt-binding resins on the morphology of rat jejunum and colon. A scanning electron microscopy study

One mechanism suggested to account for the hypocholesteremic effect of dietary fibers is their ability to sequester bile salts. Since bile salts have been found to alter intestinal structure, the morphological effects of several commonly used, xenobiotic, bile salt-binding agents was investigated. Wistar rats were fed a purified stock diet, ad libitum, for 6 weeks containing either 2% cholestyramine, 2% colestipol, or 2% DEAE-Sephadex. The bile salt-binding capacity of these substances was tested in vitro using taurocholate and glycocholate. The effect of in vivo feeding of the resins was to evoke ultrastructural topographical deviations from control appearance in both jejunal and colonic mucosae. Colonic cell injury was more severe than that observed in the jejunum of both colestipol- and DEAE-Sephadex-fed animals while the reverse was true for the rats fed cholestyramine. The degree of distortion in each condition was positively correlated with the extent of bile salt-binding capability in vitro. The rank order of both effects in terms of increasing severity was DEAE-Sephadex less than colestipol less than cholestyramine.