The role of the gut flora in the metabolism of cyclamate

1. [(14)C]Cyclamate was not metabolized when incubated with the liver, spleen, kidney or blood of rats of rabbits kept on a cyclamate-containing diet, and that had become converters of cyclamate into cyclohexylamine. 2. [(14)C]Cyclamate was converted into cyclohexylamine when incubated under anaerobic conditions with the contents of the caecum, colon or rectum or with the faeces of cyclamate-pretreated rats. Similar results were obtained with cyclamate-pretreated rabbits. With cyclamate-pretreated guinea pigs, which did not readily convert cyclamate into cyclohexylamine, the colon contents showed only low activity in this respect. 3. The faeces of a human converter of [(14)C]cyclamate into cyclohexylamine were also very active, but became less active when cyclamate was removed from his diet. 4. On subculturing the organisms from the contents of the colon and rectum of rats, the ability to convert cyclamate into cyclohexylamine was lost during three subcultures, but the loss of the activity was considerably decreased by subculturing in the presence of cyclamate. 5. Incubation of rat faeces in broths containing cyclamate increased their ability to metabolize cyclamate, but similar treatment of rabbit and human faeces suppressed this activity. 6. When rats are kept on a cyclamate diet the number of clostridia in the faeces increased considerably. In human dietary cyclamate did not appear to alter the counts of various faecal micro-organisms. 7. The gut organisms that appear to develop the ability to convert cyclamate into cyclohexylamine are clostridia in rats, enterobacteria in rabbits and enterococci in man. 8. [(14)C]Cyclohexylamine injected into the caecum or colon of rats is readily absorbed and excreted in the urine. 9. It appears that on continued intake of cyclamate the gut flora develop the ability to convert cyclamate into cyclohexylamine, which is then absorbed and excreted mainly in the urine, although a small proportion is metabolized to other compounds.     

The metabolites of cyclohexylamine in man and certain animals

1. [1-(14)C]Cyclohexylamine hydrochloride was synthesized and given orally or intraperitoneally to rats, rabbits and guinea pigs (dose 50-500mg/kg) and orally to humans (dose 25 or 200mg/person). The (14)C is excreted mainly in the urine, most of the excretion occurring in the first day after dosing. Only small amounts (1-7%) are found in the faeces. 2. In the rat, guinea pig and man, the amine is largely excreted unchanged, only 4-5% of the dose being metabolized in 24h in the rat and guinea pig and 1-2% in man. In the rabbit about two-thirds of the dose is excreted unchanged and about 30% is metabolized. 3. In the rat, five minor metabolites were found, namely cyclohexanol (0.05%), trans-3- (2.2%), cis-4- (1.7%), trans-4- (0.5%) and cis-3-aminocyclohexanol (0.1% of the dose in 24h). 4. In the rabbit, eight metabolites were identified, namely cyclohexanol (9.3%), trans-cyclohexane-1,2-diol (4.7%), cyclohexanone (0.2%), cyclohexylhydroxylamine (0.2%) and trans-3- (11.3%), cis-3- (0.6%), trans-4- (0.4%) and cis-4-aminocyclohexanol (0.2%). 5. In the guinea pig, six minor metabolites were found, namely cyclohexanol (0.5%), trans-cyclohexane-1,2-diol (2.5%) and trans-3- (1.2%), cis-3- (0.2%), trans-4- (0.2%) and cis-4-aminocyclohexanol (0.2%). 6. In man only two metabolites were definitely identified, namely cyclohexanol (0.2%) and trans-cyclohexane-1,2-diol (1.4% of the dose), but man had been given a smaller dose (3mg/kg) than the other species (50mg/kg). 7. The hydroxylated metabolites of cyclohexylamine were excreted in the urine in both free and conjugated forms. 8. Although cyclohexylamine is metabolized to only a minor extent, in rats the metabolism was mainly through hydroxylation of the cyclohexane ring, in man by deamination and in guinea pigs and rabbits by ring hydroxylation and deamination.     

Molecular weight as a factor in the excretion of monoquaternary ammonium cations in the bile of the rat, rabbit and guinea pig

1. The excretion in the bile and urine of intraperitoneally injected (14)C-labelled monoquaternary ammonium or pyridinium cations was measured in bile-duct-cannulated rats (ten compounds) and in guinea pigs and rabbits (six compounds). 2. Seven of these, namely N-methylpyridinium, tetraethylammonium, trimethylphenylammonium, diethylmethylphenylammonium, methylphenyldipropylammonium, dibenzyldimethylammonium and tribenzylmethylammonium, were excreted largely unchanged in the bile and urine. 3. 3-Hydroxyphenyltrimethylammonium, 3-bromo-N-methylpyridinium and cetyltrimethylammonium were metabolized to an appreciable extent in the rat. 4. In intact rats intraperitoneally injected trimethylphenylammonium (mol.wt. 136) was excreted mainly in the urine, dibenzyldimethylammonium (mol.wt. 226) was excreted in roughly equal amounts in the urine and faeces, and tribenzylmethylammonium (mol.wt. 302) was excreted mainly in the faeces. The faecal excretion of these compounds corresponded to their biliary excretion in bile-duct-cannulated rats. About 3-4% of tribenzyl[(14)C]methylammonium was eliminated as (14)CO(2). 5. In rats the extent of biliary excretion of four cations with molecular weights in the range 94-164 was less than 10% of the dose, whereas that of five cations with molecular weights 173-302 was greater than 10%. These results and other data from the literature suggested that the molecular weight needed for the biliary excretion of such cations to an extent of 10% or more of the dose was about 200+/-50. Studies with six cations in guinea pigs and rabbits suggest that this value applies also to these species. 6. The results suggest that the threshold molecular weight for the appreciable (>10%) biliary excretion of monoquaternary cations is different from that for anions (Millburn et al., 1967a; Hirom et al., 1972b). With rats, guinea pigs and rabbits, no significant species difference was noted, whereas with anions there is a marked species difference.     

Effects of two different loading doses of L-tryptophan on the urinary excretion of tryptophan metabolites in rats, mice and guinea pigs. Correlation with the enzyme activities

The effect of two different loading doses of L-tryptophan (0.5 and 1.0 g/Kg b.w.) on excretion of tryptophan metabolites and the relation to the enzyme activities were studied in rats, mice and guinea pigs. In rats there is no ratio between the dosage used and the levels of the metabolites excreted. Doubling the amount of tryptophan administered, a 5-fold increase in the elimination of the metabolites along the kynurenine pathway is obtained. The 1.0 g/Kg load provides a more complete pattern of the metabolites than with the 0.5 g/Kg b.w. load. Kynurenic acid, kynurenine and xanthurenic acid are the chief metabolites excreted. In mice, the urinary excretion of the metabolites is very low with both loads. In guinea pigs, xanthurenic acid is excreted in the highest amount and kynurenic acid and kynurenine also constitute the large fractions with both loadings. The load of 0.5 g/Kg b.w. is preferable to that of 1.0 g/Kg b.w. for not causing B6-deficiency. Liver tryptophan pyrrolase exists in two forms in rats, while in mice and in guinea pigs it is present only as holoenzyme. This enzyme is more active in rats than in the other two species of animals. Kynureninase activity is lower in guinea pigs, but it apparently correlated to the low levels of excretion of the metabolites following this step. Kynurenine aminotransferase is very active in rats and in mice, while it is apparently depressed in guinea pigs, in contrast with the high excretion of xanthurenic and kynurenic acids, that puts in evidence a B6-deficiency. The excretion of tryptophan metabolites and enzyme activities are better correlated in rats.     

Comparative metabolism and taurine-depleting effects of guanidinoethanesulfonate in cats,mice, and guinea pigs

Guanidinoethanesulfonate (GES) is a competitive inhibitor of taurine transport. The ability of GES to deplete taurine content has been compared in three species representing omnivores, carnivores, and herbivores. Rats and mice given drinking water containing 1% GES showed large decreases in taurine concentration in all examined organs within a few days. These species do not metabolize GES. The substance was without effect on guinea pigs, a species that does not depend on diet for taurine, even after 20 days of treatment. However, guinea pigs metabolize a fraction of the GES administered to taurine. Cats responded to GES by increasing their urinary excretion of taurine 10-fold, while simultaneously maintaining normal concentrations in body organs. [1,2-³H]GES given orally to cats was extensively metabolized to radioactive taurine. It therefore appears that the cat and to a lesser extent, the guinea pig, have transamidinase or amidinohydrolase activity for which GES is a substrate. However, this substance rapidly depletes taurine levels in the omnivores studied, and promises to be useful in further investigations on taurine in these species.     

Species variations in the biliary and urinary excretion of arsenate, arsenite and their metabolites

In most mammalian species, inorganic arsenicals are extensively biotransformed and excreted both in unchanged form and as metabolites. In the bile of rats receiving arsenate (AsV) or arsenite (AsIII) we have identified monomethylarsonous acid (MMAsIII), purportedly the most toxic metabolite of inorganic arsenic. As rats are not commonly accepted for studying arsenic metabolism, we carried out a comparative investigation on the excretion of AsV, AsIII and their metabolites in five animal species in order to determine whether they also form MMAsIII from AsV and AsIII. Anaesthetised bile duct-cannulated rats, mice, hamsters, rabbits, and guinea pigs were injected with AsV or AsIII (50 micromol/kg, i.v.) and their bile and urine was collected for 2 h. Arsenic in bile and urine was speciated by HPLC-hydride generation-atomic fluorescence spectrometry and the excretion rates of AsV, AsIII, monomethylarsonic acid (MMAsV), MMAsIII and dimethylarsinic acid (DMAsV) were quantified. All species injected with AsV excreted arsenic preferentially into urine, whereas all animals receiving AsIII, except rabbits, delivered more arsenic into bile than urine. Bile contained almost exclusively trivalent arsenic (i.e. AsIII and/or MMAsIII), whereas AsV, AsIII and DMAsV appeared in urine. Except for guinea pigs, which do not methylate arsenic, the other species formed MMAsIII and excreted it into bile. Having excreted as much as 8% of the dose of AsIII or AsV in 2 h as MMAsIII, rats were by far the most efficient producers of this supertoxic metabolite. Thus, although the rat is not a good model for studying long-term arsenic disposition, this species appears especially valuable in studies on AsIII methyltransferase and in vivo formation of MMAsIII.     

Species variations in the threshold molecular-weight factor for the biliary excretion of organic anions

1. The excretion in the bile and urine after intravenous injection of 16 organic anions having molecular weights between 355 and 752 was studied in female rats, guinea pigs and rabbits. 2. These compounds were mostly excreted unchanged, except for three of them, which were metabolized to a slight extent (<7% of dose). 3. The rat excreted all the compounds extensively (22-90% of dose) in the bile. 4. In guinea pigs four of the compounds with mol.wt. 355-403 were excreted in the bile to the extent of 7-16% of the dose, four with mol.wt. 407-465 to the extent of 25-44% and eight compounds with mol.wt. 479-752 to the extent of 44-100%. 5. In rabbits four compounds with mol.wt. 355-465 were excreted in the bile to the extent of 1-8% of the dose, two compounds with mol.wt. 479 and 495 to the extent of 24 and 22%, and six compounds with mol.wt. 505-752 to the extent of 31-94%. 6. These results, together with those of other investigations from this laboratory, are discussed and the conclusion is reached that there is a threshold molecular weight for appreciable biliary excretion (i.e. more than 10% of dose) of anions, which varies with species: about 325+/-50 for the rat, 400+/-50 for the guinea pig and 475+/-50 for the rabbit. 7. Anions with molecular weights greater than about 500 are extensively excreted in the bile of all three species. 8. That proportion of the dose of these compounds which is not excreted in the bile is excreted in the urine, and in the three species, bile and urine are complementary excretory pathways, urinary excretion being greatest for the compounds of lowest molecular weight and tending to decrease with increasing molecular weight. 9. Some implications of this interspecies variation in the molecular-weight requirement for extensive biliary excretion are discussed.     

Arginine deficiency and orotic aciduria in mammals.

Dietary arginine deficiency in rats causes significant increases in urinary excretion of urea, citric acid and orotic acid independently of feed intake. Urea excretion during arginine deficiency depends upon the diet, sex, age, and species. Thus urea excretion has limitations as an indicator of arginine availability. Although elevated urinary citric acid during arginine deficiency is more consistently observed, it may be influenced by citric acid in natural dietary ingredients. Orotic acid excretion, however, appears to be a reliable indicator of available dietary arginine based upon studies in rats, mice, hamsters, guinea pigs, rabbits, and dogs.     

Biliary excretion of some diquaternary ammonium cations in the rat, guinea pig and rabbit

1. The extent of the excretion in the bile and urine of the (14)C-labelled dications, diquat, paraquat, morfamquat, decamethonium and dimethyltubocurarine in bile-duct-cannulated rats, guinea pigs and rabbits was examined. 2. These compounds were excreted unchanged in bile and urine, except diquat, which was metabolized to a significant extent (18% of the dose) in the rabbit only. 3. The extent of the biliary excretion of diquat (mol wt. of ion 184), paraquat (186), decamethonium (258) and morfamquat (469) was less than 10% of the dose in the three species, whereas that of dimethlytubocurarine (653) was greater than 10% in the rat and rabbit but not in the guinea pig. 4. These results together with data from the literature suggest that the molecular weight at which the excretion of dications in the bile exceeds 10% of the dose is in the region of 500-600, which differs from the values for monocations (Hughes et al., 1973) and anions (Millburn et al., 1967; Hirom et al., 1972).     

Influence of intestinal bacterial desulfation on the enterohepatic circulation of dehydroepiandrosterone sulfate

Selective association of germ-free (GF) rats with dehydroepiandrosterone sulfate (DHEAS) desulfating bacteria allowed us to assess the exact impact of intestinal bacterial desulfation on the excretion and enterohepatic circulation of orally administered DHEAS. Germ-free rats selectively associated with the DHEAS-desulfating strain Peptococcus niger H4 (H4 rats) excreted 50% of the total label recovered within 17 h vs 21 h in GF rats and 13 h 23 min in conventional (CV) rats. Germ-free rats excreted 30% of the total label recovered via their urine. However, association of GF rats with the desulfating microorganism increased urinary excretion to 46%, comparable to the 45.5% found in CV rats. Fractionation of fecal label yielded 70% sulfoconjugated DHEAS and 2% unconjugated dehydroepiandrosterone in GF rats vs 5 and 77% in CV rats, and 55 and 14% in H4 rats, respectively. Our results demonstrate that the intestinal bacterial desulfation of DHEAS stimulated the enterohepatic circulation of DHEAS. This in turn increased the urinary excretion of label resulting in an accelerated elimination of labeled DHEAS from the body.     

Effect of dietary protein, alfalfa, and zeolite on excretory patterns of 5',5',7',7'-[3H]zearalenone in rats

A series of experiments was conducted to determine how dietary protein, alfalfa, or zeolite influence the excretory patterns of zearalenone (Z), a uterotropic mycotoxin synthesized by Fusarium fungi. Rats were fed diets containing 16.3% casein, 40% casein, 11.2% casein + 25% alfalfa, or 25% casein + 25% alfalfa. Also fed were diets containing 0, 1, 2, or 5% anion exchange zeolite. Tracer doses of [3H]Z were administered either as a constituent of the diet or as a topical application on the skin at the base of the skull. When Z was administered orally, no differences were seen in the fraction of the dose excreted in urine or feces as a result of varying dietary levels of alfalfa and protein. Topical doses resulted in rats fed 25% casein + 25% alfalfa or 40% casein excreting more Z in urine than those fed 25% alfalfa or 16.3% casein. Fecal excretion of Z was greatest for rats fed 25% casein + 25% alfalfa whereas rats fed 40% casein excreted more fecal Z than those fed 16.3% casein. Feeding Z to rats receiving dietary zeolite resulted in a positive correlation between dietary zeolite and fecal excretion of Z but a negative correlation with urinary excretion of Z. Topical administration of Z produced a positive correlation between dietary zeolite and fecal Z excretion but no effect on urinary excretion. It may be concluded that protein and alfalfa treatments alleviate Z toxicosis through increased metabolism whereas zeolite binds Z in the digestive tract to prevent absorption.     

Chemotherapeutic Evaluation of Clotrimazole [Bay b 5097, 1 (o-Chloro-α-α-Diphenylbenzyl) Imidazole]

Clotrimazole has a broad spectrum of activity against yeast and filamentous fungi in vitro and also in vivo when given orally or parenterally to experimentally infected mice and when administered orally or topically to infected guinea pigs. In vitro a distinct inoculum effect has been observed with a number of strains of Candida and Torulopsis; minimal inhibitory concentrations have tended to increase with increased incubation time. With prolonged incubation times, resistance can be developed to clotrimazole in vitro, but this resistance is readily reversible upon passage in drug-free broth. The degree of in vivo activity of clotrimazole against Candida depends on the severity of infection used. Orally it appears to be more effective when administered by gavage than when given mixed in the diet. Pretreatment with the agent may decrease its efficacy because of drug inactivation. Against dermatophytes, clotrimazole has a degree of activity similar to griseofulvin when given orally, but it is less active than tolnaftate topically in cutaneous infection of Trichophyton mentagrophytes in guinea pigs. In vitro, but not in vivo, some gram-positive and gram-negative bacteria are inhibited by low concentrations of clotrimazole.     

Intestinal Absorption of Tritium-Labelled Folic Acid in Idiopathic Steatorrhea: Effect of a Gluten-Free Diet

The intestinal absorption of folic acid in patients with idiopathic steatorrhea was studied by the oral administration of tritium-labelled folic acid in a dosage of 15 μg./kg. Results were expressed as a percentage of the orally administered folic acid radioactivity excreted in the urine over 24 hours. The mean excretion of radioactivity in 38 normal subjects was 48.2 ± 16.6% (mean ± SD), whereas eight patients with untreated idiopathic steatorrhea excreted only 16.7 ± 3.4% (mean ± SE).The ability of the gluten-free diet to correct this absorptive defect was demonstrated by the finding of normal values in 11 patients in complete clinical remission for periods exceeding six months after institution of the diet. Serial studies in individual patients indicated that a significant improvement was obtainable in as short a period as two weeks following exclusion of gluten from the diet.     

Comparison of tracheal mucous transport in rats, guinea pigs, rabbits, and dogs

Tracheal mucous transport was measured using similar techniques in several species. One- to 10-microliter quantities of 99mTc-macroaggregated albumin (99mTc-MAA) were instilled via oral intubation in the distal trachea of rats, rabbits, and dogs. Tracheostomies were used for the instillation in guinea pigs. All animals were anesthetized with halothane for the instillation and allowed to recover immediately in restrainers. Clearance of the 99mTc-MAA in rats and guinea pigs was measured by a slit-collimated NaI scanner. In rabbits and dogs a series of gamma-camera scintiphotos were taken. Clearance was faster and more efficient in dogs than in the other species. No significant differences existed among the rats, rabbits, and guinea pigs in the percentages of the originally deposited material remaining at the instillation site after 1 h (P greater than 0.2). Mean values and standard deviations were 83 +/- 23%, 81 +/- 22% and 70 +/- 20% for rats, guinea pigs, and rabbits, respectively. However, in the dogs a mean of 14 +/- 12% remained at the original site of deposition after only 25 min indicating much more rapid clearance. Mean leading-edge velocities were 9.8 +/- 2.1 (SD) for dogs, 3.2 +/- 1.1 for rabbits, 2.7 +/- 1.4 for guinea pigs, and 1.9 +/- 0.7 mm/min for rats. Clearance patterns qualitatively among the species. In dogs the material moved as a few discrete boluses, whereas in the other species the activity spread toward the larynx. The relatively slow mucous transport of rats, rabbits, and guinea pigs could have important implications in inhalation toxicological studies.     

Anti-cholestatic activity of HD-03, a herbal formulation in thioacetamide (TAA)-induced experimental cholestasis

In the present study HD-03, a herbal formulation was investigated for its anti-cholestatic activity in TAA-induced cholestasis in anaesthetized guinea pigs. Administration of TAA at a dose of 100 mg/kg body wt significantly reduced the bile flow, bile acid and bile salt excretion. Pretreatment with HD-03 at a dose of 750 mg/kg body wt per orally for 15 days in guinea pigs significantly prevented thioacetamide-induced changes in bile flow, bile acids and bile salts excretion. Thus, HD-03 can serve as a potent choleretic and anti-cholestatic agent.     

Ixodes dammini: Induced skin lesions in guinea pigs and rabbits compared to erythema chronicum migrans in patients with lyme arthritis

Erythematous skin lesions occurred in rabbits 2 days after being fed upon by larvae or nymphs of the tick, Ixodes dammini. Similar lesions occurred in guinea pigs 7 days after a primary infestation with either larvae or nymphs. Host resistance to secondary feeding by larvae was demonstrated in guinea pigs and rabbits. Host resistance to secondary feeding by nymphs was seen in guinea pigs, but not in rabbits. Guinea pigs developed resistance to nymphs after being previously fed upon twice by larvae. All skin lesions in resistant guinea pigs contained large accumulations of basophils (49–76% of cells) with smaller (20–33%), but significant, numbers of eosinophils. These responses were characteristic of strong cutaneous basophil hypersensitivity reactions. Primary and secondary lesions in rabbits fed upon by larvae contained mostly mononuclear cells (46–52%) and moderate numbers (16–30%) of basophils and eosinophils. Primary and secondary lesions in rabbits fed upon by nymphs had few (3–11%) basophils and eosinophils and were dominated by mononuclear cells (73–86%). Thus, acquired resistance in guinea pigs and rabbits was associated with cutaneous basophil and eosinophil responses and the lack of resistance of rabbits to nymphs was associated with erythematous lesions dominated by mononuclear cells. The mononuclear nature of rabbit lesions induced by nymphal feeding was similar to that seen in erythema chronicum migrans in Lyme arthritis patients who are thought to have been fed upon by I. dammini nymphs. This study confirms the cutaneous basophil hypersensitivity characteristics of lesions in guinea pigs resistant to ticks and demonstrates a relationship between the mononuclear cell response of rabbits to nymphal I. dammini and the cellular response seen in patients with erythema chronicum migrans and Lyme arthritis.     

Comparative study of ethynyloestradiol metabolism in the rabbit, guinea pig and rat.

Ethynyloestradiol was administered to rabbits, guinea pigs and rats, and the concentration of the steroid in blood was measured by radioimmunoassay. In both rabbits and guinea pigs, levels of conjugated steroid were much higher than those of the freely extractable form. Whereas considerable amounts of steroid were present in a congugated form in plasma 24 h after injection, none was present at this time in a freely extractable form. There were significant differences between young and adult rabbits and guinea pigs in the rate at which ethynyloestradiol was metabolized. The amounts present in the freely extractable form in rats were higher than in the other two species but no steroid was detected in the conjugated fraction. The results are compared with previous findings in humans.     

Comparison of synthetic saponin cholesterol absorption inhibitors in rabbits: evidence for a non-stoichiometric, intestinal mechanism of action

The hypocholesterolemic activities of pamaqueside and tiqueside, two structurally similar saponins, were evaluated in cholesterol-fed rabbits. The pharmacological profiles of the saponins were virtually identical: both dose-dependently decreased the intestinal absorption of labeled cholesterol 25-75%, increased fecal neutral sterol excretion up to 2.5-fold, and decreased hepatic cholesterol content 10-55%. High doses of pamaqueside (>5 mg/kg) or tiqueside (>125 mg/kg) completely prevented hypercholesterolemia. Decreases in plasma and hepatic cholesterol levels were strongly correlated with increased neutral sterol excretion. Ratios of neutral sterol excreted to pamaqueside administered were greater than 1:1 at all doses, in opposition to the formation of a stoichiometric complex previously suggested for tiqueside and other saponins. Ratios in tiqueside-treated rabbits were less than unity, a reflection of its lower potency. Pamaqueside-treated rabbits exhibited a more rapid decline in plasma cholesterol concentrations than control animals fed a cholesterol-free diet, indicating that the compound also inhibited the absorption of biliary cholesterol. Intravenous administration of pamaqueside had no effect on plasma cholesterol levels despite plasma levels twice those observed in rabbits given pamaqueside orally.These data indicate that pamaqueside and tiqueside induce hypocholesterolemia by blocking lumenal cholesterol absorption via a mechanism that apparently differs from the stoichiometric complexation of cholesterol hypothesized for other saponins.     

Effect of wheat bran on excretion of radioactively labeled estradiol-17 beta and estrone-glucuronide injected intravenously in male rats.

Urinary and fecal estrogen excretion were studied in male rats fed a non-fiber wheat starch diet (dietary fiber less than 1%; NF group; n = 4), a low-fiber wheat flour diet (dietary fiber 2%; LF group; n = 4) or a high-fiber wheat bran diet (dietary fiber 11.6%; HF group; n = 3). Short-term effects of the experimental diet on estrogen excretion were studied after i.v. injection of 5 microCi (0.185 MBq) of [14C]estradiol-17 beta (E2) into the tail vein of the rats fed the diets for 2 days. After 3 weeks on the experimental diets, the long-term effects were studied after injection of 5 microCi of [14C]E2 and 10 microCi of [3H]estrone-3-glucuronide (E1-gluc). The diet was found to affect estrogen excretion. The short-term effect indicated that rats fed the HF diet excreted a relatively large amount of labeled compounds in the feces during the first day after injection, while rats fed the NF or the LF diets excreted about half that amount over the same period. On the other hand, urinary excretion of labeled compounds was significantly higher in the NF and LF rats. The long-term effect resulted in steeper slopes (P less than 0.05) of the fecal excretion profiles of rats fed the HF diet as compared with rats fed the NF and LF diets, indicating an accelerated fecal excretion of labeled compounds in the HF rats. The kinetic profiles of 14C and 3H radioactivity in blood plasma indicated a fast decrease (t1/2 of less than 2 min) for both [14C]E2 and [3H]E1-gluc. It was concluded that, owing to the short-term effect of wheat bran intake, during the first 24 h after i.v. administration relatively large amounts of radioactively labeled compounds are excreted in feces of rats fed the HF diet. In contrast, excretion is lower in urine of these rats. When the microflora is adapted to the experimental diet the wheat bran diet still results in an accelerated fecal excretion of labeled compounds, which might be attributed to an interruption of the enterohepatic circulation of estrogens. This might result in lowered plasma and/or tissue estrogen levels and hence a decreased exposure of estrogen-sensitive tissue to estrogens, which might decrease risk on mammary (breast) cancer development.     

Metabolism of sialic acids from exogenously administered sialyllactose and mucin in mouse and rat

A mixture of N-acetyl-[4,5,6,7,8,9-14C]neuraminosyl-alpha (2-3(6]-galactosyl-beta (1-4-glucose[( 14C]sialyl-lactose) and N-acetylneuraminosyl-alpha (2-3(6]-galactosyl-beta(1-4)-glucit-1-[3H]ol(sialyl-[3H]lactitol) as well as porcine submandibular gland mucin labeled with N-acetyl- and N-glycoloyl-[9-(3)H]neuraminic acid were administered orally to mice. The distribution of the different isotopes was followed in blood, tissues and excretion products of the animals. One half of the [14C]sialyl-lactose/sialyl-[3H]lactitol mixture given orally was excreted unchanged in the urine. The other half was hydrolysed by sialidase and partly metabolized further, followed by the excretion of 30% of the 14C-radioactivity as free N-acetyl-[4,5,6,7,8,9-14C]neuraminic acid and 60% of this radioactivity in the form of non-anionic compounds including expired 14CO2 within 24 h. The 14C-radioactivity derived from the [14C]sialyl-lactose/sialyl-[3H]lactitol mixture which remained in the bodies of fasted mice after 24 h was less than 1%. In the case of well-fed mice, a higher amount of the sialic acid residues was metabolized. The bulk of radioactivity of the mucin was resorbed within 24 h. About 40% of the radioactivity administered was excreted by the urine within 48 h; 30% of this radioactivity represented sialic acid and 70% other anionic and non-anionic metabolic products. 60% of the radioactivity administered remained in the body, and bound 3H-labeled sialic acids were isolated from liver. Sialyl-alpha (2-3)-[3H]lactitol was injected intravenously into rats; the substance was rapidly excreted in the urine without decomposition. These studies show that part of the sialic acids bound to oligosaccharides and glycoproteins can be hydrolysed in intestine by sialidase and be resorbed. This is followed either by excretion as free sialic acid or by metabolization at variable degrees, which apparently depends on the compound fed and on the retention time in the digestive tract.