Rat intestinal sucrase. II. The effects of rat age and sex and of diet on sucrase activity.
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Animals↗
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Dietary stimulation of sucrase in a patient with sucrase-isomaltase deficiency.
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Carbohydrate Metabolism, Inborn Errors↗
Evidence of degradation process of sucrase-isomaltase in jejunum of adult rats.
To evaluate degradation processes of sucrase-isomaltase in adult rat jejunum, we determined enzymic activity of sucrase and isomaltase and compared it with the amount of immunoreactive sucrase-isomaltase. In rats fed or starved for 18h, killed at 10:00 h or 22:00 h, sucrase activity (expressed on the basis of total protein or of immunoreactive sucrase-isomaltase) was significantly (P less than 0.02) lower in the lower jejunum than in the upper jejunum; isomaltase activity was similar in both segments. Crossed immunoelectrophoresis demonstrated the existence of a second sucrase-isomaltase antigen reacting with anti-(sucrase-isomaltase) serum. This antigen was present in larger amounts in the lower jejunum than in the upper jejunum, exhibited immunological partial identity with the intact sucrase-isomaltase, and had isomaltase activity but no sucrase activity. Results suggest that this antigen is a degradation product of sucrase-isomaltase in which the sucrase active site has been broken down. To examine the role of pancreatic enzymes in degradation of sucrase-isomaltase, common pancreatico-biliary ducts were ligated. Within 18 h after the operation, the difference of sucrase activity between the upper and the lower jejunum disappeared and the amount of the second sucrase-isomaltase antigen markedly decreased in the lower jejunum. Our results indicate that, during the degradation of intestinal sucrase-isomaltase by the pancreatic proteinases, degradation of the sucrase active site precedes that of the isomaltase active site.
Animals↗
Characterization of degradation process of sucrase-isomaltase in rat jejunum with monoclonal-antibody-based enzyme-linked immunosorbent assay.
As shown previously, during degradation of sucrase-isomaltase in rat jejunum, degradation of the sucrase active site occurs before that of isomaltase active site [Goda & Koldovský (1985) Biochem. J. 229, 751-758]. To characterize further the process of sucrase-isomaltase degradation in jejunum, we determined the amounts of immunoreactive sucrase-isomaltase in rat jejunum by using a monoclonal-antibody-based enzyme-linked immunosorbent assay. By employing two alternative monoclonal antibodies (one reacting with the sucrase subunit and the other reacting with the isomaltase subunit), the amount of antigen-containing sucrase subunit and the amount of antigen-containing isomaltase subunit were separately quantified. In both upper and lower jejunum of rats, the amount of antigen-containing isomaltase subunit was always higher than the amount of antigen-containing sucrase subunit. This difference was attributable mainly to a degradation product of sucrase-isomaltase, which was identified as isomaltase monomer. Occlusion of pancreatic ducts for 18 h eliminated the difference between the amount of antigen-containing sucrase subunit and the amount of antigen-containing isomaltase subunit in both upper and lower jejunum. In jejunum of control animals, the molar ratio of sucrase subunit to isomaltase subunit was estimated to be 0.32-0.52, indicating that quite a large proportion of sucrase-isomaltase (48-68%) is present as degradation products (e.g. isomaltase monomer). These results support the model of degradation process of sucrase-isomaltase in brush-border membranes of rat jejunum, whereby degradation of sucrase subunit by the action of pancreatic proteinase(s) precedes degradation of isomaltase subunit.
Animals↗
Quantitative relationship between intestinal sucrase inhibition and reduction of the glycemic response to sucrose in rats.
We have investigated the quantitative relationship between sucrase inhibition and reduction in the 0-3 h glycemic response to an oral dose of sucrose in rats. Castanospermine is a quasi-irreversible sucrase inhibitor that did not dissociate from sucrase during tissue preparation or assay for sucrase activity. An oral dose of castanospermine (0.1-3.0 mg/kg body wt) dose-dependently reduced sucrase activity of intestinal segments by 15-90%; 0.4 mg/kg body wt reduced total sucrase activity about 50%. The lower doses inhibited sucrase much more extensively in the proximal than in the distal segments. Castanospermine also dose-dependently reduced the 0-3 h glycemic response to sucrose; 1.5 mg/kg body wt reduced the glycemic response about 50%. Each submaximal castanospermine dose inhibited total sucrase activity more than it reduced the glycemic response. We conclude that intestinal sucrase activity in the rat is in modest excess relative to the rate-determining step of glucose absorption following sucrose administration. Fourteen days of castanospermine treatment (0.2 mg.kg body wt-1.d-1) resulted in sucrase inhibition that was similar to a single castanospermine treatment, suggesting that castanospermine treatment resulted in neither cumulative sucrase inhibition nor induction of sucrase activity.
Alkaloids↗
Expression of enzymatically active sucrase-isomaltase is a ubiquitous property of colon adenocarcinomas.
Adenocarcinoma of the colon is one of the most prevalent and lethal of all human malignancies. The early diagnosis and management of this disease could be improved if biological markers, whose expression was restricted to malignant colon cells, were identified. Sucrase-isomaltase is a glycoprotein hydrolase expressed throughout the small intestine and fetal colon but not in the normal adult colon. This study shows that the expression of enzymatically active sucrase-isomaltase is a ubiquitous property of primary and metastatic colon adenocarcinoma. Significant sucrase enzyme activity (i.e., greater than 5 mU/mg protein) was observed in 16 colon carcinomas but not in adjacent normal colon mucosa. Sucrase-isomaltase messenger RNA was identified in all tumors using reverse transcriptase polymerase chain reaction. Using a quantitative polymerase chain reaction analysis, this study shows that the amount of sucrase-isomaltase messenger RNA in tumors examined (3.4 x 10(-8) to 3.19 x 10(-7) micrograms/micrograms total RNA) was greater than in adjacent mucosa (0 to 3.4 x 10(-8) micrograms/micrograms total RNA). This induction of sucrase-isomaltase messenger RNA and enzyme activity was corroborated by immunostaining. Of 30 colon adenocarcinomas examined, 80% were positive for sucrase-isomaltase. In addition, all colon carcinoma metastases examined were positive for sucrase-isomaltase. The staining pattern was distinct and demarcated tumor cells from the surrounding histologically normal tissue. No sucrase-isomaltase staining was seen in normal mucosa from the same patients. With the exception of lung, no sucrase-isomaltase immunostaining was observed in a variety of examined noncolonic adenocarcinomas. Thus, the specificity and ubiquity of sucrase-isomaltase expression in adenocarcinomas of the colon can be exploited to improve the clinical management of this disease. In addition, studies on the structure of the sucrase-isomaltase gene and its regulatory elements should contribute toward understanding the alteration of gene expression by oncogenic transformation of the colonic mucosa.
Adenocarcinoma↗
The intestinal brush border membrane in diabetes. Studies of sucrase-isomaltase metabolism in rats with streptozotocin diabetes.
Diabetes stimulates the functional activity of the intestinal brush border membrane with enhancement of both hydrolytic enzyme activity and membrane transport systems. To determine the mechanism of this effect, we studied the effects of streptozotocin diabetes on the metabolism of one membrane protein, sucrase-isomaltase, which increases its activity in diabetes. The protein was purified and an antiserum prepared. Sucrase-isomaltase from control and diabetic rats was immunologically identical as shown by Ouchterlony double-diffusion analysis of papain-solubilized mucosal proteins. The increase in sucrase enzyme activity in diabetic animals (31.0+/-1.4 U SEM 5 days after streptozotocin vs. 13.1+/-1.0 in controls) was the consequence of increased enzyme protein and not an alteration in catalytic efficiency as demonstrated by quantitative immunoprecipitin reactions. To account for increased sucrase-isomaltase protein in diabetes we studied papain-solubilized mucosal proteins labeled by injection of [(14)C]carbonate and [(14)C]leucine and analyzed incorporation into sucrase-isomaltase protein (anti-serum precipitable) and total protein (trichloroacetic acid precipitable). We found that diabetes did not affect the decay of labeled total protein, but prolonged the decay of labeled sucrase-isomaltase. t((1/2)) of sucrase-isomaltase was 4.4 h in control animals after [(14)C]carbonate injection and 8.8 and 10.2 h, respectively, 2 and 5 days after induction of streptozotocin diabetes. We obtained similar results in experiments with [(14)C]leucine with diabetes increasing t((1/2)) from 6 to 13.6 h. Diabetes did not appear to increase the rate of addition of sucrase-isomaltase to the brush border membrane, since it did not affect the 10- and 60-min incorporations of isotope into sucrase-isomaltase protein relative to incorporation into total protein and did not alter rate constants for synthesis calculated from the t((1/2)) and the change in enzyme mass over time.Thus, enhanced sucrase activity in the diabetic animal is the consequence of an increase in sucrase-isomaltase protein which develops because of a decrease in its rate of degradation.
Animals↗
Differential expression of sucrase-isomaltase in clones isolated from early and late passages of the cell line Caco-2: evidence for glucose-dependent negative regulation.
The expression of the brush border-associated hydrolase sucrase-isomaltase was shown to increase from early to late passages of Caco-2 cells, concomitant with a decrease in the rates of glucose consumption. Twenty-six clones were isolated from early (P29) and late (P198) passages of the cell line. These clones show considerable and inverse differences in the levels of sucrase activities and rates of glucose consumption, without marked changes in other features of enterocytic differentiation of the cells (presence of an apical brush border, levels of expression of other brush border-associated hydrolases). Clones with low sucrase-isomaltase expression show a mosaic expression of the enzyme and a 38-fold higher rate of glucose consumption than clones with high sucrase-isomaltase expression. The clones with high expression show an homogeneous apical distribution of the enzyme and 70-fold and 35-fold higher levels of sucrase activities and sucrase-isomaltase mRNA, respectively. In contrast no differences were found from one clone to another in the enrichment of sucrase activity in brush border-enriched fractions as compared to cell homogenates. Switch to low glucose-containing medium (1 mM versus 25 mM in standard culture conditions) of cells with low sucrase-isomaltase results in an increased and more homogeneous expression of the enzyme and a tenfold augmentation of the levels of sucrase-isomaltase mRNA and sucrase activity. These results show that glucose interferes with the expression of sucrase-isomaltase in Caco-2 cells at the mRNA level.
Adenocarcinoma↗
Brush border membrane sucrase-isomaltase, maltase-glucoamylase and trehalase in mammals. Comparative development, effects of glucocorticoids, molecular mechanisms, and phylogenetic implications.
1. Trehalase, sucrase-isomaltase and maltase-glucoamylase are three integral glycoproteins of the brush border membranes of the enterocytes. On the basis of a comparative study on alpha-glycosidase activities (sucrase, isomaltase, maltase, glucoamylase and trehalase) associated to these glycoproteins during neonatal development, mammals could be basically divided into three groups. 2. In rodents and rabbit alpha-glycosidase activities are low or undetectable during the suckling period and increase to adult levels during the weaning period. In cat, dog and the primates examined, alpha-glycosidase activities are well or fully developed at birth. 3. In ruminants and pinnipedia alpha-glycosidases are low or absent throughout life. 4. During the suckling period of rat, mouse and rabbit, glucocorticoids trigger a premature and dramatic increase of all alpha-glycosidases. 5. On the contrary, alpha-glycosidases development during the weaning period appears to be independent of glucocorticoids. Neither hypophysectomy nor adrenalectomy prevent the development of alpha-glycosidases; only the rate of increase is reduced. 6. Transplantations of intestinal isografts either in adult or suckling animal, have shown that (1) no systemic factor inhibits the expression of alpha-glycosidase, (2) alpha-glycosidases induction is neither triggered by luminal alimentary substances, nor by hormones, (3) alpha-glycosidase development is controlled by an intrinsic ontogenic program. 7. The use of an antiglucocorticoid failed to inhibit the spontaneous development of alpha-glycosidase activities. 8. The increase of maltase and sucrase activities triggered by glucocorticoids is associated with an increase of the concentration of two glycoproteins in the microvillous membrane: sucrase-isomaltase and maltase-glucoamylase. 9. After administration of glucocorticoids the increase of maltase, sucrase and trehalase is strongly inhibited by actinomycin-D and the increase of sucrase activity is associated with a parallel increase of sucrase-isomaltase mRNA. Transcription is most likely the primary site of control of alpha-glycosidase biosynthesis. 10. In the crypt cells, alpha-glycosidases biosynthesis appears to be triggered by a receptor-mediated glucocorticoid interaction. 11. The enterocytes synthesize more alpha-glycosidase molecules as they travel to the tip of the villi. 12. The simultaneous, biosynthesis of sucrase-isomaltase and maltase-glucoamylase triggered by glucocorticoids, as well as their simultaneous normal development suggest that they may be subjected to related control mechanisms. 13. It is suggested that sucrase-isomaltase and maltase-glucoamylase might have arisen by several cycles of partial gene duplication of an ancestor gene coding for a single site maltase-isomaltase; subsequent mutation would have transformed isomaltase into sucrase or glucoamylase.
Animals↗
Cell migration and cortisone induction of sucrase activity in jejunum and ileum.
The increase of sucrase activity in homogenates of jejunum and ileum of suckling rats after cortisone administration has been investigated. Serial tissue sections of villi and crypts were also assayed for sucrase activity and these results were compared with the migration of cells labelled with [(3)H]thymidine along the villus. By using a low dose of cortisone (0.5mg/day per 100g body wt.) it was found that the sensitivity of the small intestine producing system to cortisone stimulation increased during the suckling period. On the other hand, 5mg of cortisone/day per 100g body wt. produced practically the same increase of sucrase during the entire suckling period. Sucrase activity in homogenates of the entire small-intestinal wall was first detected 24h after the first injection of cortisone (5mg/day per 100g body weight) to 9-day-old animals and maximum activity both in the jejunum and ileum was reached by 120h. Jejunal activity was greater than ileal activity, but the rate of the increase was similar. The half-time of the increase was 23-27h, whereas enterocytes migrate from the base to the tip of the villi in approximately 72h. Comparison of sucrase activity in serial tissue sections of villi and crypts at various times after cortisone treatment showed that the leading edge of sucrase activity proceeds toward the tip of the villi at the same rate as the advancing edge of newly formed cells. Sucrase activity increased in the newly induced cells as they migrated to the tip of the villi. It was concluded that the increase of sucrase activity in suckling rats after cortisone stimulation is due to at least three factors: (1) increase of activity in newly differentiating cells, (2) increased percentage of villus cells with sucrase activity and (3) continued production or activation of sucrase activity as the cells migrate along the villi.
Age Factors↗
Expression of sucrase-isomaltase mRNA along the villus-crypt axis in the rat small intestine.
Sucrase-isomaltase has been used as a marker enzyme to study cell differentiation along the intestinal villus-crypt axis. Previous studies are in agreement that sucrase activity is confined to villus epithelial cells. However, immunoreactivity data are at conflict, with some studies reporting sucrase antigen in crypts as well as villi. To resolve this discrepancy, our goal was to determine the distribution of sucrase-isomaltase mRNA. A cDNA clone representing 3.0 kb of rat sucrase-isomaltase, including the sucrase active site, was characterized. Northern analysis of 12 tissues demonstrated a 6 kb transcript only in the small intestine. Jejunal cell fractions prepared by a washing technique showed declining levels of both sucrase activity and sucrase-isomaltase mRNA as well as increasing levels of thymidine kinase activity from early to later fractions. Since later fractions did not yield pure crypt cells, in situ hybridization using an 35S-labeled sucrase-isomaltase riboprobe was performed. The transition from zero to intense signal at the crypt-villus junction leads us to conclude that in the adult rat, sucrase-isomaltase gene expression is initiated only after cells leave the proliferative cycle and migrate onto the villi.
Amino Acid Sequence↗
Chick embryo intestine in culture: influence of insulin and other hormones on sucrase, maltase, and alkaline phosphatase.
The development of alkaline phosphatase, maltase, and sucrase activities in the duodenum of the chick embryo was followed in organ culture in chemically defined medium; 14-day duodenum was used in most experiments, with comparisons being made with 18-day tissue. As has been previously shown for the other enzymes, sucrase activity also rises at an accelerated rate in vitro. Since chick sucrase has maltase activity, its increase appears to account for the spontaneous rise of maltase activity; the form of maltase devoid of sucrase activity seems not to be accelerated. Sucrase, sucrase-free maltase, and alkaline phosphatase are all elevated by the addition of insulin to the medium. Intestinal sucrase is well known to be responsive to hydrocortisone, but it has now been found to be unresponsive to thyroxine, except that its dissociation from the brush border is increased at hormone concentrations above 1 nM. Insulin and thyroxine act synergistically on alkaline phosphatase, but the addition of hydrocortisone diminishes the effect of the other two. With sucrase, insulin and hydrocortisone have a synergistic effect which is intensified by addition of thyroxine. The previously demonstrated influence of hydrocortisone on maltase is accounted for by the maltase activity of sucrase. In combination, however, hydrocortisone and thyroxine elevated maltase much more strongly than sucrase, and the highest maltase levels were attained when all three hormones were present.
Alkaline Phosphatase↗
Sucrase-alpha-dextrinase in the rat. Postinsertional conversion to inactive molecular species by a carbohydrate-free diet.
Absence of dietary carbohydrate decreases both activities of intestinal brush border sucrase-alpha-dextrinase. We examined the molecular mechanism causing this decrease. Adult rats were fed chow (70% CHO) or matched carbohydrate-free (CHO-free) diet for 7 d. Sucrase activity decreased by 50% in whole homogenates and brush borders. Enzyme kinetics revealed no change in sucrose affinity (CHO-free Km = 18 mM, chow Km = 21 mM), but fewer active sites (CHO-free Vmax = 2,720, chow Vmax = 5,000 mumol/min per g protein). Intraintestinal pulse-labeling of [35S]methionine in vivo revealed no differences in incorporation into sucrase. Immunoreactive sucrase protein, assayed by ELISA and rocket immunoelectrophoresis, increased twofold per milliunit of sucrase enzymatic activity in CHO-free jejunum. Total immunosucrase (St), the sum of active and inactive enzyme (St = Sa+Si), was unchanged with carbohydrate withdrawal, but > 50% of the sucrase protein became inactive. SDS-PAGE of sucrase immunoprecipitates revealed alteration of alpha, beta, and gamma subunits in CHO-free animals: (a) alpha and beta subunits migrated farther (mass change--2 kD); and (b) the alpha subunit became diffuse or was a doublet and was less abundant than the beta subunit. Rather than representing loss of sucrase protein, the decline in sucrase activity is achieved with structural subunit changes, probably involving postinsertional processing.
Animals↗
Feeding medium-chain triglycerides to rats decreases degradation of sucrase-isomaltase complex in the jejunum.
We demonstrated previously that feeding a diet containing medium-chain triglycerides (MCT) to rats causes an increase in the sucrase activity in jejunum relative to diets containing long-chain triglycerides (LCT). To explore the mechanism whereby MCT affect jejunal sucrase activity, 7-wk-old rats were fed a high LCT diet for 7 d, and then they were force-fed either the high LCT diet, a high MCT diet or a high carbohydrate (alpha-methylglucoside) diet for the subsequent 12 h. Feeding the high carbohydrate diet produced significantly greater sucrase and isomaltase activities in both upper and lower jejunum than feeding the LCT diet. Feeding the high MCT diet led to significantly greater sucrase activity in the lower jejunum, but isomaltase activity was not elevated. Rocket immunoelectrophoresis revealed that in the lower jejunum of the rats fed the high MCT diet the proportion of sucrase-isomaltase complex to its degradation product (i.e., isomaltase monomer) was elevated, suggesting that dietary MCT affects sucrase activity by retardation of degradation of sucrase-isomaltase. Because the amounts of total bile acids in the upper jejunum were 50% lower in rats fed the high MCT diet relative to animals fed the high LCT diet, it is likely that MCT feeding decreases secretion of bile into the lumen, which in turn decreases degradation of the sucrase subunit of the sucrase-isomaltase complex.
Animals↗
Regulation of lactase and sucrase-isomaltase gene expression in the duodenum during childhood.
BACKGROUND: In children, lactase and sucrase-isomaltase are essential intestinal glycohydrolases, and insufficiency of either enzyme causes diarrhea and malnutrition. Little is known about the regulation of lactase and sucrase-isomaltase expression in the duodenum during childhood. In this study, the mechanisms of regulation of duodenal expression of both enzymes were examined in a study population with ages ranging from 1 to 18 years. METHODS: Duodenal biopsy specimens from 60 white children were used to analyze tissue morphology and to quantify lactase and sucrase-isomaltase mRNA and protein. RESULTS: Among healthy subjects, high interindividual variability was noted in both mRNA and protein levels for lactase and sucrase-isomaltase. Lactase mRNA level per subject did not correlate with sucrase-isomaltase mRNA level and thus appeared independent. Both lactase and sucrase-isomaltase protein levels correlated significantly with their respective mRNA levels. For each enzyme, a significant inverse correlation was observed between the degree of villus atrophy and mRNA levels. Aging from 1 to 18 years did not result in significant changes in mRNA or protein levels of either enzyme. Immunostaining patterns within the duodenal epithelium for lactase differed from sucrase-isomaltase in adjacent sections, illustrating independent regulation at the cellular level. CONCLUSIONS: In the duodenum of white children, lactase and sucrase-isomaltase seem primarily regulated at the transcriptional level. The expression of each enzyme in the intestinal epithelium is regulated by an independent mechanism. Lactase and sucrase-isomaltase exhibit stable mRNA and protein levels in healthy children as they grow to adulthood. Mucosal damage affected levels of both enzymes negatively.
Adolescent↗
Sucrase and maltase activities in supragingival dental plaque in humans of streptococcal, actinomyces and lactobacilli species.
20 reference strains and 72 isolated strains from dental plaque of streptococci, actinomyces, and lactobacilli species were examined for sucrase and maltase activities. The type of sucrase in the different strains was determined by use of the alpha-glucosidase inhibitor, acarbose. The enzyme activities were determined as formation of monosaccharide, and quantitated spectrophotometrically. Although variations occurred in enzyme activities between reference and isolated strains, the same general pattern was noticed. Strains of Streptococcus mutans and S. salivarius showed regularly the highest sucrase activities, followed by strains of Actinomyces viscosus and A. naeslundii. Most lactobacilli belonged to the bacteria with low sucrase activity like S. sanguis and S. mitior. In some lactobacilli strains, however, a high sucrase activity was observed. The level of sucrase activity in S. mutans strains was dependent on biotype/serotype, as strains of biotype V/serotype e showed high activities, biotypes I and IV corresponding to serotypes c, f, and d showed intermediate activity, and biotype III/serotype a always showed low activity. In most of the strains the sucrases were composed of enzymes with specificity against both alpha-glucosidic linkage and beta-fructosidic linkage of the sucrose molecule, but in varying ratios. In all species, exept S. sanguis and S. mitior, lower maltase than sucrase activity was observed, but even in the two species mentioned the maltase activities were relatively low. On the basis of observations of selected reference strains in every species examined both sucrases and maltases are to some extent inducible.
Actinomyces↗
Site of substrate stimulation of jejunal sucrase in the rat.
To identify the site of stimulation of sucrase by a sucrose diet, changes in sucrase-specific activity of jejunal mucosa were studied after introduction of sucrose diet to carbohydrate-deprived rats. Results were correlated with simultaneous changes in villus gradients of sucrase-specific activity. Simultaneous with the introduction of sucrose diet, [(3)H]thymidine (100 muCi) was administered intravenously, and rates of cell migration measured during adaptation to the new diet. After a 72-h fast, rats fed sucrose diet for 6, 12, or 18 h showed no change in sucrase-specific activity in either whole mucosa or villus gradients. However, within 18-24 h after starting a sucrose diet, there was a marked rise in whole mucosal sucrase-specific activity above fasting values (99 +/- 14 vs. 38 +/- 4 muM glucose/min per g protein, P < 0.001) in association with the development of a region of increased activity at the lower villus (154 +/- 22 vs. 60 +/- 9 muM glucose/min per g protein, P < 0.02, but with no change in villus tip activity (56 +/- 5 vs. 46 +/- 8 muM glucose/min per g protein). Similar changes were seen in animals fed 24 h of sucrose diet after a 72-h carbohydratefree diet. Fasted animals fed sucrose diet for 36 h had increased sucrase-specific activity at the villus tip (144 +/- 11 muM glucose/min per g protein) as well as at the lower villus region, and this pattern persisted at 1 wk of sucrose diet. Maximal activity patterns for isomaltase and maltase paralleled those for sucrase, but the villus gradients for lactase were unaffected by sucrose diet. The region of maximal sucrase-specific activity always coincided with or followed the leading edge of radioactivity as determined by liquid scintillation counting. Therefore, sucrose-mediated changes in sucrase activity of the jejunal mucosa in the rat appear to be initiated at the level of the crypt epithelial cell and are expressed after a latent period of 18-24 h during which these cells mature and migrate toward the villus tip.
Animals↗
Effect of feeding amaranth (food red no. 2) on the jejunal sucrase and digestion-absorption capacity of the jejunum in rats.
To clarify the effect of feeding 5% amaranth (Food Red No. 2, Am) alone or with 5% dietary fiber on jejunal mucosal integrity, change in jejunal sucrase activity before and after the feeding was compared between rats fed and fasted previously. Digestion-absorption capacity of the jejunum was also examined by perfusing 15 mmol/liter sucrose and 30 mmol/liter glycylglycine through the anesthetized rat jejunum after 14 days of feeding Am. Gobo dietary fiber (GDF) was prepared from the roots of edible burdock (Arctium lappa L.). At the end of 3 days' fasting, rats had 20% less body weight, 30% less mucosal protein and 50% less jejunal sucrase activity per unit length than those before fasting. Although rats fed Am showed severe diarrhea and growth retardation as observed in previous reports, initial sucrase level was not changed by feeding Am for 3 days even in the fasted rats. When sucrase activity on day 3 after feeding was compared among inter-groups, however, rats fed Am showed sucrase activity lower than that of rats fed either the basal diet or the basal diet containing Am plus GDF only when they had been fasted previously. After 14 days of feeding, rats fed Am after 3 days' fasting regained sucrase activity up to that of rats fed the basal diet despite the remarkable growth retardation. Jejunal perfusion in situ showed that digestion-absorption capacity for sucrose and glycylglycine in rats fed 5% Am for 14 days was also the same as that in rats fed the basal diet. These results suggest that feeding Am can reduce neither jejunal sucrase nor digestion-absorption capacity of epithelial cells of the jejunum, but retards the regain of the lowered sucrase level at earlier stage of feeding when rats have been fasted before the feeding, and that concurrent feeding of GDF promotes catch-up of the sucrase level lowered by the fasting.
Amaranth Dye↗