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Physicochemical characterization and biological effects of inulin enzymatically synthesized from sucrose.

We first developed the method to produce inulin from sucrose using an enzyme from Bacillus sp. 217C-1. Synthesized inulin consists of a linear polymer having beta(2-1) linkages of d-fructose with one terminal glucose. The synthesized inulin has similar properties (pH and thermal stability, Maillard reaction, and in vitro fermentation) to plant-derived inulin. The marked difference is the polydispersity of the inulin chain length. Synthesized inulin with a narrow degree range of fructose polymerization shows better solubility in water than plant-derived inulin. Synthesized inulin (5%, w/w) treatment for 12 weeks reduced the elevation in body weight and serum and liver lipids in rats fed high fat- and high sucrose-supplemented diets, and blood glucose in rats fed a standard diet. Synthesized inulin (15%, w/w) significantly suppressed the elevation in blood glucose of human healthy subjects after dextrin loading. These results suggest that daily intake of synthesized inulin modulates carbohydrate and lipid metabolism.

Animals↗

Disposition of 3H-cholesteryl ether labeled liposomes following intravenous administration to mice: comparison with an encapsulated 14C-inulin as aqueous phase marker.

In this study, the blood clearance and organ distribution of intravenously administered liposomes (distearoyl phosphatidylcholine [DSPC] and cholesterol in a ratio of 3:1) was evaluated by utilizing 3H-cholesteryl ether as the lipid phase marker. Also, the ability of liposomes, as a drug delivery system, to alter the distribution and retention of encapsulated agents was investigated by comparing the distribution of intravenously administered free and liposome-encapsulated 14C-inulin within a 48-hr postadministration period. Intravenously administered DSPC liposomes were distributed in all organs examined with the highest levels of 3H-cholesteryl ether and 14C-inulin present in the liver and spleen; peak levels occurred 3 hr postadministration (71.86% +/- 9.39 versus 77.67% +/- 10.30, respectively, in the liver and 5.05% +/- 1.07 versus 5.36% +/- 1.09, respectively, in the spleen) declining gradually during the remaining experimental period. The lowest levels of 3H-cholesteryl ether and 14C-inulin following administration of liposome-encapsulated inulin were found in the lung, kidney, and heart. The area under curve showed much more accumulation of 14C-inulin (6-fold higher) in the body following administration of the liposome-encapsulated drug than the free drug. The ratio of 3H to 14C following administration of liposome-encapsulated inulin was constant throughout the entire observation period, suggesting that the disposition of inulin acquired both the carrier's rate of clearance and tissue distribution. These results indicated that following intravenous administration of liposome-encapsulated inulin, the majority of the radioactively labeled formulation was retained by the organs of the reticuloendothelial system (liver and spleen); liposomes greatly enhanced the retention of inulin in the body; and the liposomal formulation did not destabilize and subsequently did not release the encapsulated inulin to the tissues and organs.

Animals↗

Excretion of major odor-causing and acidifying compounds in response to dietary supplementation of chicory inulin in growing pigs.

The excretion of major odor-causing and acidifying compounds in response to dietary supplementation of chicory inulin extract was investigated with six Yorkshire barrows, with an average initial BW of 30 kg, according to a balanced two-period cross-over design. The animals were fed a control diet containing no inulin extract and a treatment diet with 5% inulin extract (as-fed basis) at the expense of cornstarch. Each diet was formulated (as-fed basis) to contain 16% CP from corn (51%) and soybean meal (29%). Each experimental period lasted 14 d, with 10 d for dietary adaptation and 4 d for collection of fecal and urine samples. The fecal samples were analyzed for four major classes of odor-causing and acidifying compounds: 1) VFA; 2) N-containing compounds, including total N and ammonia; 3) volatile sulfides measured as hydrogen sulfide units; and 4) phenols and indoles, including p-cresol, indole, and skatole. Supplementation of chicory inulin at 5% had no effects on the fecal excretion of VFA (P = 0.29), ammonia (P = 0.96), total volatile sulfides (P = 0.56), p-cresol (P = 0.56), and indole (P = 0.75). Fecal excretion of total N (inulin = 6.13 vs. control = 5.10 g/kg DMI) was increased (P < 0.05), whereas urinary total N excretion (inulin = 15.1 vs. control = 16.4 g/[pig x d]) was not affected (P = 0.17) by the inulin supplementation compared with the control group. Furthermore, fecal excretion of skatole (inulin = 9.07 vs. control = 18.93 mg/kg DMI) was decreased (P < 0.05) by the inulin supplementation compared with the control group. In conclusion, dietary supplementation of 5% chicory inulin extract is effective in decreasing the fecal excretion of skatole in growing pigs fed corn and soybean meal diets.

Ammonia↗

Practical approach for determining glomerular filtration rate by single-injection inulin clearance.

We compared the glomerular filtration rate as measured by a single-injection inulin clearance with that measured by a standard isotope method with 99mTc-labeled diethylenetriaminopentaacetic acid in 21 subjects with glomerular filtration rates greater than 35 mL/min. After a bolus injection of 5 g of inulin, blood samples were taken 20, 45, 90, 120, 145, 180, and 240 min afterwards. Inulin was measured by optimized chemical or enzymatic methods of high analytical sensitivity to determine inulin at low concentrations. We used the one-compartment model and inulin concentrations measured at two sampling times to calculate the glomerular filtration rate from the data of the disappearance curve of inulin. Inulin concentrations at 20 and 240 min after injection of the inulin bolus were suited to estimate glomerular filtration rate by this procedure, resulting in values (y) comparable with those obtained by isotope technique (x). The relationship to the isotope technique was characterized by the equation y = +4.80 mL/min + 0.92x (r = 0.97). The single-injection inulin clearance determination can detect a decrease of glomerular filtration rate at the beginning of kidney damage, given that our study included subjects with glomerular filtration rates greater than 35 mL/min. We conclude that the glomerular filtration rate can be determined by analyzing only two blood samples after a bolus injection of inulin.

Adult↗

Promotion of intestinal tumor formation by inulin is associated with an accumulation of cytosolic beta-catenin in Min mice.

Inulin, polydisperse beta (2-1) fructan, has been suggested to protect against colon carcinogenesis and is currently used in a number of food applications. However, the data regarding the role of inulin in intestinal carcinogenesis remains controversial since the results of our previous study suggested that inulin promotes intestinal tumor formation in Min mice, an animal model for intestinal cancer with a mutation in the Apc tumor suppressor gene (Carcinogenesis 2000;21:1167-73). In our present study, we further examined the effects of inulin on intestinal tumor formation in Min mice by carefully analyzing beta-catenin expression and cellular localization at 3 different time points during the tumorigenic process. Min mice were fed a high-fat inulin-enriched (10% w/w) diet or the high-fat diet without any added fiber from the age of 6 weeks to the ages of 9, 12 or 15 weeks. The results showed that inulin significantly increased the number (by 20%) and especially the size (by 44%) of adenomas in the small intestine. At week 15, the promotion of tumor development was accompanied by an accumulation of cytosolic beta-catenin in the adenoma tissue. In the normal appearing mucosa, levels of membrane beta-catenin and PCNA were reduced in the inulin-fed mice, possibly indicating impaired enterocyte migration. These data do not support the earlier suggestions on the cancer preventive effects of inulin and emphasize the need for further research and evaluation where health claims for inulin are concerned.

Adenoma↗

Anti-complementary action of polymorphic "solubility forms" of particulate inulin.

Inulin crystallizes in a series of polymorphic forms with different solubility rates, ranging from one instantly soluble at 23 degrees C (beta 0(23) inulin) through a form soluble at 37 degrees C with a half-time of 8 min (alpha 8(37) inulin) to a form virtually insoluble at 37 degrees C (gamma inulin). All forms are interconvertible, the more soluble and unstable progressing on standing to less soluble and more stable forms, only reversible by complete solution followed by recrystallization. The end product is the stable gamma inulin, only formed by polymers greater than 8000 mol. wt. A method is given for preparing pure "gamma inulin for injection", comprising insoluble ovoids of less than 1 micron diameter free of soluble inulin and endotoxin. An assay developed for complement action by the alternative pathway showed that gamma inulin was the most potent activator polymorph, more active than killed S. aureus and zymosan. Dissolved inulin and the more soluble polymorphs were inactive and in a mixture hindered alternative pathway activation by the gamma form.

Chromatography, DEAE-Cellulose↗

Cecal parameters of rats fed diets containing grapefruit polyphenols and inulin as single supplements or in a combination.

OBJECTIVE: We compared the effects of grapefruit flavonoids and inulin, as single dietary components or in a combination, on cecal fermentation in rats adapted to a semipurified diet. METHODS: The experimental diets contained 0.3% flavonoid extract and 5% or 10% inulin and a combination of both supplements. The large bowel metabolism assessment was based on cecal parameters: bulk effect, pH, microbial enzymes activity, and short-chain fatty acid production. RESULTS: Both supplements induced significant enlargement of the cecal digesta weight. Acidification of cecal digesta was more pronounced, with a higher inulin addition to the diet. Cecal pH was the highest with the flavonoid-rich diets and lowest in the case of a simultaneous addition of flavonoids and a high content of inulin. The flavonoid extract applied as a single dietary supplement was observed to decrease the activity of bacterial beta-glucosidase and beta- and alpha-galactosidases in the cecal digesta. In contrast, addition of the grapefruit extract to inulin-containing diets increased the activity of alpha-glucosidase, alpha-galactosidase, and beta-galactosidase. Great accumulation of cecal digesta in rats consuming the flavonoid-diet caused a considerable increase in the short-chain fatty acid pool, mainly acetic acid. Inulin added to the diet decreased the excessive enlargement of digesta caused by dietary flavonoids. Dietary addition of inulin to the flavonoid-diet also normalized hydration of cecal digesta and significantly decreased the pH of digesta. The presence of polyphenols in the inulin-containing diets did not change total short-chain fatty acid production in the cecum of rats. CONCLUSION: Our results suggested that simultaneous intake of inulin and polyphenols can decrease the detrimental effects of the latter on cecal fermentation.

Adaptation, Physiological↗

Transfer of inulin across the first-trimester human placenta.

OBJECTIVE: Our aim was to investigate the transfer of inulin from the mother to the first-trimester fetus. STUDY DESIGN: A bolus of inulin (5 mg/kg) was administered to nine healthy volunteers with pregnancies between 6 and 12 weeks of gestation scheduled for elective termination of pregnancy. Coelomic and amniotic fluid samples were obtained from the corresponding cavities between 8 and 25 minutes after the end of the bolus of inulin. Fetal fluid inulin concentrations were compared with those of matched samples of maternal blood and urine collected simultaneously. RESULTS: Inulin was detected in all fetal and maternal samples. A trend toward an increasing inulin concentration was noted in the exocoelomic cavity with advancing time. Coelomic and maternal serum inulin concentrations were similar within 20 minutes after injection. Amniotic inulin concentrations were always lower than coelomic concentrations irrespective of gestational age or advancing time after injection. CONCLUSIONS: Inulin crosses the first-trimester human placenta from 7 weeks of gestation in quantities that yield measurable concentrations in both coelomic and amniotic fluids. These results suggest that the study of drug transfer in the first trimester of human pregnancy is feasible with use of samples obtained from the exocoelomic cavity.

Female↗

Inulin as filler-binder for tablets prepared by direct compaction.

The tabletting properties of a number of different amorphous inulin types were investigated. The types varied with respect to chain length, particle size and amount of included air in the particles. Powder flow properties and densities of the different types were investigated. Just as expected, it was found that the flow properties improved with increased particle size of the material. Compactibility was investigated by compression of tablets on a compaction simulator, simulating the compression on high-speed tabletting machines. The bonding capacity of all inulins was high. However, the lubricant sensitivity strongly varied among the different types of inulin. Generally, amorphous materials such as starches are highly lubricant sensitive, because they show ductile behaviour upon compaction. On the other hand, crystalline materials such as dicalcium phosphate dihydrate have a low lubricant sensitivity, because they fragment during compaction. A high lubricant sensitivity was indeed found for amorphous inulins with a low amount of entrapped air. In contrast, the lubricant sensitivity of the amorphous inulin was low when particles containing large amounts of air were compressed. Obviously entrapped air induces fragmentation of the powder particles by which the lubricant film, covering the particles, was destroyed. Tablets prepared from inulin did not disintegrate but they dissolved when incubated in water. The disintegration/dissolution time increased with decreasing chain length of the inulin. The addition of a disintegrant reduced the disintegration time. The somewhat slower dissolution of the longer chain inulin can be an advantage for chewable tablets or lozenges. It was concluded that inulin with large amounts of entrapped air is a good filler-binder and an attractive alternative to commonly used filler-binders.

Chemistry, Pharmaceutical↗

Inulin hydrogels as carriers for colonic drug targeting. Rheological characterization of the hydrogel formation and the hydrogel network.

Free radical polymerization converts aqueous solutions of methacrylated inulin into cross-linked hydrogels. The purpose of this work was to study the hydrogel formation and to characterize the fully cured hydrogels. The gelation process of aqueous solutions of methacrylated inulin was monitored as a function of time by means of linear oscillatory shear measurements, at a fixed frequency and amplitude. The fully cured inulin hydrogels were characterized by measurement of the frequency-dependency of the linear elastic modulus G'. The effects of the degree of substitution and feed concentration of methacrylated inulin on both the gelation kinetics and the rigidity of the obtained hydrogels were determined. The effect of the concentration of the initiators of the radical polymerization reaction has been studied as well. The weight fraction of polymer which was not incorporated in the hydrogel networks was determined using the anthrone reaction, and physical chain entanglements were determined by solution viscosity measurements. The gelation kinetics and the elastic modulus were proportional to the degree of substitution and feed concentration of methacrylated inulin. Increasing concentrations of radical-forming compounds also accelerated the hydrogel formation, but lowered the elastic modulus of the obtained hydrogels. The amount of polymer chains incorporated in the hydrogel network seemed to be especially influenced by the degree of substitution of the derivatized inulin, and for a feed concentration of 27% w/w of methacrylated inulin, entanglements have to be accounted for. The gelation kinetics and the elastic modulus of inulin hydrogels are not only affected by the degree of substitution and the feed concentration of methacrylated inulin, but also by the concentration of the initiators of the free radical polymerization reaction.

Algorithms↗

Comparison of inulin with urea as dilutional markers of bronchoalveolar lavage in healthy and heaves-affected horses.

Solute analysis in bronchoalveolar lavage fluid involves the use of dilutional markers to correct for variable recovery of pulmonary epithelial lining fluid (PELF). Urea is the best characterised endogenous marker, whereas inulin appears to meet the requirements of an exogenous marker. In horses, the use of inulin has never been investigated and the impact of lower airway diseases such as heaves, on PELF recovery is unknown. In this study, five healthy and five heaves-affected horses underwent airway endoscopy and bronchoalveolar lavage. PELF recovery from bronchoalveolar lavage was calculated by the inulin and the urea method. The inulin method was compared to the urea method and differences between healthy and heaves-affected horses were analysed. From a technical and analytical point of view, inulin fulfilled the requirements of a marker of dilution as well as urea. When both healthy and heaves-affected horses groups were pooled together, PELF recovery calculated by the inulin method was significantly higher than by the urea method (6.43+/-4.08% versus 0.789+/-0.299%, P < 0.005). No significant differences were observed between healthy and heaves-affected horses, neither by the inulin nor by the urea method. Inulin did not present major advantages over urea, but the combined use of both markers can improve the standardisation of studies comparing PELF compounds, by providing upper limits (inulin dilution) and lower limits (urea dilution) of PELF recovery.

Animals↗

Dietary inulin intake and age can significantly affect absorption of the faecal marker dysprosium in rats.

It is believed that rare earth elements are not absorbed, and thus they are generally used in some mineral absorption studies as a faecal marker. The aim of the present study was to determine the effect of inulin intake and age on dysprosium (Dy) absorption in rats. Eighty male Wistar rats of four different ages (2, 5, 10 and 20 months) were randomised into either a control group or a group receiving 3.75 % inulin in their diet for 4 d and then 7.5 % inulin until the end of the study. The animals were fed fresh food and water ad libitum for 30 d. The intestinal absorption of Dy was determined from a 4 d (day 21 to day 25) balance study. Mean faecal Dy recovery (%) in the eight groups (3 months control, 3 months inulin, 6 months control, 6 months inulin, 11 months control, 11 months inulin, 21 months control, 21 months inulin) was 94.0 (sd 8.6), 64.8 (sd 10.1), 95.8 (sd 9.4), 81.5 (sd 12.1), 98.4 (sd 9.8), 87.8 (sd 9.5), 97.8 (sd 6.2) and 84.9 (sd 10.9), respectively. Our results showed clearly that dietary inulin intake decreased faecal Dy recovery in all four rat groups, and faecal Dy recovery was significantly higher in the old rats (10 and 20 months) than in the young and adult rats. These results show that the faecal recovery (or intestinal absorption) of Dy may vary greatly with nutritional or physiological states such as inulin intake or age. The use of rare earth elements as a faecal marker should be thus validated under each nutritional or physiological state before being employed in mineral absorption studies.

Age Factors↗

Physiological effects of lactulose and inulin in the caecum of rats.

A model experiment was performed on rats to evaluate the effect of partial or total substitution of saccharose (S) and cellulose (C) by preparations of lactulose and inulin on the development and metabolism of the caecum. In the experimental diets given to rats for 4 weeks, the examined preparations were administered either with an equivalent amount of cellulose (each at 4% of the diet) or as sole source of dietary fibre at 8% of the diet. Compared to the saccharose group cellulose had no effect, and low doses of lactulose and inulin in the diet increased to a medium extent the weight of the caecum wall and caecal digesta. The addition of lactulose and inulin at 8% increased significantly the content of caecal digesta (4.62 and 4.11 g/100g BW, respectively) and the weight of the caecal wall (1.10 and 0.86 g/100g BW, respectively), compared to the groups with saccharose and cellulose (0.73, 0.90 and 0.24, 0.28 g/100g BW, respectively). Cellulose and cellulose partially-substituted with lactulose and inulin caused an increase in the dry matter content of caecal digesta (26.5-27.5%), compared to other groups (21.8-22.8%). The administration of lactulose and inulin preparations was accompanied by a significant drop in pH (5.47-5.81), compared to the groups with cellulose or saccharose (6.83-6.91), and a decrease in the ammonia concentration in the caecal digesta, compared to the cellulose control (0.27-0.40 and 0.62 mg/g, respectively). The group with 8% lactulose was characterized by the highest activities of microbiological alpha- and beta-galactosidase and beta-glucosidase in the caecal digesta. Cellulose and both preparations significantly decreased the activity of beta-glucuronidase, compared to the saccharose group (0.39-0.89 and 1.52 U/g, respectively). The highest concentration of VFA in the caecal digesta was observed in the saccharose group (89.2 micromol/g), and the lowest concentration in the group where cellulose was totally substituted by lactulose and inulin (55.1 and 57.5 micromol/g, respectively). The total production of VFA in the caecum was fourfold higher with 8 % lactulose and inulin (254.7 and 236.4 micromol/100g BW, respectively) than in both controls groups (65.1 and 67.8 micromol/100g BW, respectively). The high dose of inulin and lactulose increased the share of propionic acid in the VFA profile (C2:C3:C4) compared to both control groups. When 4% inulin was added to the diet a significant increase of butyrate concentration in the caecum was observed.

Animals↗

On the presence of inulin and oligofructose as natural ingredients in the western diet.

The classic definitions of inulin and oligofructose are constructively criticized. It is observed that inulin cannot unequivocally be described as a polydisperse 1-kestose-based (GFn) beta (2-->1) linear fructan chain, but that inulin always contains small amounts of Fm and branched molecules. This review article describes the presence of inulin and oligofructose in common foodstuffs. Historical data on human consumption add an extra dimension. Modern analytical techniques (HPLC, LGC, HPAEC-PAD) are used to check the variety of data mentioned in the literature throughout the past century. Methods to determine inulin and oligofructose in natural foodstuffs (cereals, fruit, and vegetables) are optimized and used to determine the loss of inulin during storage and during preparation of the food. These findings allow quantification of the amount of inulin and oligofructose in the average daily western diet. The daily per capita intake is estimated to range from 1 to 10 g, depending on geographic, demographic, and other related parameters (age, sex, season, etc.). Inulin and oligofructose are not measured by classic methods of dietary fiber analysis and consequently are often not mentioned in food tables. Their significant contribution (1 to 10 g/d/per capita) to the dietary fiber fraction (recommended at 25 g/d/per capita) is not taken into account in any nutritional recommendations. In view of this, inulin and oligofructose deserve more attention, both in food composition tables and in diet or nutrition studies.

Diet↗

The functional capacity of hypertrophied nephrons. Effect of partial nephrectomy on the clearance of inulin and PAH in the rat.

A method is described for the measurement of inulin and PAH clearances in rats without killing the animal. Inulin clearance measurements of partially nephrectomized rats and sham-control rats were made before operation and at intervals following the operation; inulin clearances were determined on normal rats at intervals during their growth. In another series of partially nephrectomized rats and their sham-operated controls, inulin and PAH clearances were determined in all the animals before and at intervals following the operation. Glomerular counts were made in some rats. After partial nephrectomy the inulin clearance is reduced but not as much as would be expected considering the amount of renal tissue removed. The mean inulin clearance per nephron is greatly increased in the partially nephrectomized rat when compared to the value determined for the control rat. The inulin clearance of the partially nephrectomized rat shows a progressive decline which is first clearly evident about 6 months after operation. The sham-operated rats showed an inulin clearance slightly less than that of nonoperated controls about 24 to 30 wk after the operation. In the normal rats the inulin clearance relative to body weight is much greater in rats with a mean weight of 197 +/- 3 g than in normals which are older and heavier. The PAH dearance of the partially nephrectomized rat is reduced following operation but undergoes no further change in the ensuing 24 wk.

Aminohippuric Acids↗

Dietary inulin improves distal colitis induced by dextran sodium sulfate in the rat.

OBJECTIVES: Inulin stimulates intracolonic generation of butyrate and growth of lactic acid bacteria. This study investigated whether inulin protects against colitis. METHODS: Rats with dextran sodium sulfate colitis received inulin either orally (1% in drinking water, or 400 mg/day) or by enema. Matched groups received vehicle. In addition, fecal water obtained from inulin-fed rats was administered by enema to rats with colitis and compared with fecal water from control rats. Finally, rats with colitis received daily enemas of either butyrate (at 40 or 80 mmol/L) or vehicle. Inflammation was assessed by eicosanoid asssay in rectal dialysates and MPO activity in colonic tissue. Mucosal lesions were blindly scored by microscopic examination. Luminal pH was measured from cecum to rectum by a surface microelectrode. RESULTS: Oral inulin prevented inflammation, as evidenced by lower lesion scores (p < 0.05), decreased release of mediators (p < 0.05), and lower tissue MPO (p < 0.05) as compared with controls. Inulin induced acidic environment (pH <7.0) from cecum to left colon and increased counts of lactobacilli. Fecal water from inulin-fed rats also reduced scores (p < 0.05) and inflammation (p < 0.05). However, inulin or butyrate enemas had no effect. CONCLUSIONS: Oral inulin reduces the severity of dextran sodium sulfate colitis. The effect seems to be mediated by modification of the intracolonic milieu.

Animals↗

Addition of inulin to breakfast does not acutely affect serum ionized calcium and parathyroid hormone concentrations.

BACKGROUND/AIMS: The aim of the present study was to investigate the effects of inulin on calcium metabolism. The study consisted of two separate parts both of which had a randomized two-period cross-over design. METHODS: Fifteen young healthy women volunteered to participate in this study. During the first part of the study, cheese containing 210 mg of calcium, either with 15 g of inulin or without any inulin, was ingested at breakfast, and in the second part, 210 mg of calcium as a supplement, either with 15 g inulin or without inulin, was ingested. The whole day's diet was standardized. Before breakfast, and 2, 4, 6 and 8 h after breakfast, a blood sample was taken, and intact parathyroid hormone (iPTH), ionized calcium (iCa) and total calcium were measured. Urine was collected throughout the day, and the 8-, 12- and 24-hour calcium excretion was calculated. RESULTS: The iPTH or iCa concentration curves (AUCs) did not differ over 8 h, whether or not inulin was consumed at breakfast. The postload urinary calcium excretion was not affected by the inulin. CONCLUSION: Fifteen grams of inulin in fresh cheese or with a calcium supplement (210 mg Ca) taken at breakfast does not acutely affect the markers of calcium metabolism as opposed to a corresponding breakfast without inulin.

Adult↗

The anti-melanoma activity of inulin in mice.

Finely divided, insoluble inulin (gamma polymorph), given intraperitoneally (i.p.) to C57BL mice 1-3 days after i.p. B16 melanoma cells, very significantly increased their mean survival time (MST) in low doses (less than or equal to 40 and less than or equal to 100 micrograms/mouse in 50 and 80% of tests, respectively). The gamma inulin was pure and free of endotoxin and soluble inulin, and was developed as a potent reagent specific for activating the alternative pathway of complement (APC). Its antitumour action paralleled its in vitro APC activation, namely, both activities were sharply dose-dependent up to a threshold dose above which they were dose-independent; dissolved inulin was inactive in vitro and in vivo, decreased the MST of the mice and in a mixture antagonized the in vitro and in vivo activities of gamma inulin; the more soluble (alpha) polymorphs were active in proportion to their gamma content but the effects were blocked at higher doses presumably by dissolved inulin. In addition, depletion of host APC with cobra venom factor or inulin before giving B16 cells increased their malignancy and abrogated the subsequent antitumour action of gamma inulin. The minimum i.p. dose of gamma inulin found to activate serum APC in vivo was 50 micrograms (2.5 mg/kg), i.e. close to the minimum antitumour dose. These close correlations and the specificity of the reagent indicate that activation in vivo of the APC (cellular or humoral) is an important first contact in stimulating host antitumour defences in this mouse model.

Animals↗