Cortisol increases the activities of intestinal apical membrane hydrolases and nutrient transporters before weaning in mink (Mustela vison)

Glucocorticoids from endogenous and exogenous sources accelerate maturation of brush-border membrane (BBM) hydrolases in omnivorous laboratory rodents and pigs. Less is known for carnivores, and whether the route of administration (oral or systemic) has an influence. The present study examined the influence of administering cortisol (hydrocortisone succinate, 5 mg/kg-day) to mink during postnatal week 4, just prior to weaning, on small intestine glucose and amino acid (aspartate, leucine, lysine, methionine, proline) absorption and on the activities of BBM disaccharidases and peptidases. Kits treated with cortisol were smaller (P<0.05), but had small intestines that were proportionally larger (P<0.05 for length and mass per kg body weight, but not for mucosal mass) than control kits with higher rates of absorption for most nutrients, except leucine, and increased activities of most BBM hydrolases, except lactase. As a consequence, cortisol increased hydrolytic and absorptive capacities of the entire small intestine, with the responses more pronounced when the cortisol was given orally. These findings indicate administration of cortisol stimulates growth of the developing mink small intestine, but does not accelerate the postnatal declines in nutrient transport, and may be a dam-to-kit signal that prepares suckling mink to digest and absorb the adult diet.     

Dietary flavonoid and isoflavone glycosides are hydrolysed by the lactase site of lactase phlorizin hydrolase

Lactase phlorizin hydrolase (LPH; EC 3.2.1.62) is a membrane-bound, family 1 beta-glycosidase found on the brush border of the mammalian small intestine. LPH, purified from sheep small intestine, was capable of hydrolysing a range of flavonol and isoflavone glycosides. The catalytic efficiency (k(cat)/K(m)) for the hydrolysis of quercetin-4'-glucoside, quercetin-3-glucoside, genistein-7-glucoside and daidzein-7-glucoside was 170, 137, 77 and 14 (mM(-1) s(-1)) respectively. The majority of the activity occurred at the lactase and not phlorizin hydrolase site. The ability of LPH to deglycosylate dietary (iso)flavonoid glycosides suggests a possible role for this enzyme in the metabolism of these biologically active compounds.     

Alpha-Glutamyl-beta-naphthylamide hydrolase of rabbit small intestine. Localization in the brush border and separation from other brush border peptidases.

About 70% of the total mucosal enzymatic activity hydrolyzing beta-L-glutamyl-beta-naphthylamide in the rabbit small intestine is present in the brush border; the specific activity in this subcellular fraction is 7 times higher than that of the homogenate. Similar results are obtained for L-leucyl beta-naphthylamide hydrolase. The enzyme activity is efficiently solubilized by papain digestion and is clearly separated from L-leucyl-beta-naphthylamide hydrolase by chromatography on concanavalin A-Sepharose. It probably represents a digestive peptidase, different from the other known peptide hydrolases of the digestive surface of the small intestine.     

Delayed effects of protein deficiency in nutrition of the pregnant rats on development of the enzymatic system in digestive and nondigestive organs of offspring

It has been found for the first time that protein deficit in female's nutrition during prenatal development of the offspring is accompanied by considerable changes in the activity of intestinal digestive enzymes and of the same hydrolases in the colon, liver and kidneys both in early and in late ontogenesis. It seems possible that changes of the small intestine enzyme functions and hydrolytic functions of other digestive and non-digestive organs in result of an unfavorable early "metabolic/nutritional programming" may be crucial in disorders of metabolic processes leading to development of diseases of risk in adult life.     

α-Glutamyl-β-naphthylamide hydrolase of rabbit small intestine: Localization in the brush border and separation from other brush border peptidases

About 70% of the total mucosal enzymatic activity hydrolyzing α-l-glutamyl-β-naphthylamide in the rabbit small intestine is present in the brush border; the specific activity in this subcellular fraction is 7 times higher than that of the homogenate. Similar results are obtained for l-leucyl-β-naphthylamide hydrolase.The enzyme activity is efficiently solubilized by papain digestion and is clearly separated from l-leucyl-β-naphthylamide hydrolase by chromatography on concanavalin A-Sepharose. It probably represents a digestive peptidase, different from the other known peptide hydrolases of the digestive surface of the small intestine.     

Substrate specificity of small-intestinal lactase. Assessment of the role of the substrate hydroxyl groups.

Lactase-phlorizin hydrolase is a disaccharidase present in the small intestine of mammals. This enzyme has two active sites, one being responsible for the hydrolysis of lactose. Lactase activity is thought to be selective towards glycosides with a hydrophilic aglycon. In this work, we report a systematic study on the importance of each hydroxyl group in the substrate molecule for lactase activity. For this purpose, all of the monodeoxy derivatives of methyl beta-lactoside and other lactose analogues are studied as lactase substrates. With respect to the galactose moiety, it is shown here that HO-3' and HO-2' are necessary for hydrolysis of the substrates by lactase. Using these chemically modified substrates, it has been confirmed that lactase does not behave as a typical beta-galactosidase, since it does not show an absolute selectivity with respect to substitution and stereochemistry at C4' in the galactose moiety of the substrate. However, the glucose moiety, in particular the HO-6, appears to be important for substrate hydrolysis, although none of the hydroxyl groups seemed to be essential. In order to differentiate both activities of the enzyme, a new assay for the phlorizin-hydrolase activity has also been developed.     

小鼠小肠四种消化酶活力的胎后发育模式

为明确晚成型小鼠胎后发育肠道消化酶活力的建立过程和发育模式,探讨其与适应性调节假说的关系,测定了从出生后至27日龄小鼠小肠前、中、后段的乳糖酶、蔗糖酶、麦芽糖酶和氨基肽酶的酶活力。结果发现单位组织酶活力方面,乳糖酶活力先增后降,小肠前段在9日龄而中后段在12日龄达到最高,至27日龄时仅中段有微弱的酶活力;蔗糖酶活力12日龄始出现,前段和后段自15日龄迅速升高,至18日龄达最高,但随后显著降低,而中段在15日龄后持续升高至21日龄达到最高,此后维持在较高水平;麦芽糖酶出生时已具有活力,但在15日龄前维持较低水平,此后迅速升高,前后段在18日龄,中段在21日龄达到峰值,此后下降;小肠前段的氨基肽酶活力出生后至27日龄持续下降,而后段和中段从出生到断乳前则持续升高,断乳后略有下降。除乳糖酶总酶活力先增后降,在15日龄达峰值外,其余3种酶的总酶活力均持续增加。在小肠不同位置4种酶活力的分布具有显著差异,且日龄对不同位置酶活力的影响趋势不同。总之,小鼠小肠4种消化酶的酶活力随时间的变化能够与其食物转变的消化需求相匹配,部分地支持适应性调节假说。     

Formation of the Digestive-Transport Conveyer of Carbohydrates in Rat Ontogenesis

The absorption of free glucose and glucose released from hydrolysis of different oligosaccharides has been studied using the procedure of perfusion of the isolated segment of the small intestine of rat pups, with the simultaneous determination of activities of intestinal disaccharidases by glucoseoxidase method. It has been established that: (1) the active transport of glucose in the small intestine is sufficiently pronounced during the breast feeding and gradually decreases by the time of transition of the pups to the definitive nutrition; (2) at this period, activities of lactase and of lactase-transport complexes are rather high, with the low level of activities of maltase and of maltase-transport ensembles, or complexes; (3) during the transition to the definitive feeding, simultaneously with the lactase activity repression, the activity of the lactase-transport ensembles is reduced, and digestive-transport complexes are formed, which provide high rates of hydrolysis of carbohydrates, the main component of the food.     

Functioning of Enzyme Systems of Digestive and Non-Digestive Organs in Adult Rats Depends on Quality of Nutrition in Early Ontogenesis

It is revealed that restriction of protein in nutrition of rat pups in early ontogenesis, at the period of transition from the mixed to the definitive nutrition, produces change of structural parameters and functioning of digestive enzymes in various parts of small intestine (duodenum, jejunum, and ileum) and in large intestine as well as of these hydrolases in liver and kidney in adult life. The disturbance of quality of nutrition in early ontogenesis seems to affect negatively digestive functions of small intestine and trophic-barrier function of large intestine, liver, and kidney, which can promote development of diseases not only of the gastrointestinal tract, but also of other organs.     

Changes in the functions of the intestinal brush border membrane during the development of the ruminant habit in lambs

1. Brush border membrane vesicles were prepared from lamb enterocytes. These were used to study the changes in the enzyme contents and the transport capacities which occur during the change from a milk to a roughage diet. 2. Na+-dependent transport of D-glucose was present in all regions of the small intestine of pre-ruminant lambs and absent in ruminants. 3. Na+-dependent transport of L-proline was present in all regions of the small intestine irrespective of the age of the animal. 4. Phosphate transport was seen only in the presence of a transmembrane pH gradient (acid outside). The transport was not stimulated by either Na+ or K+. The transport capacity increases 2-fold as the animal becomes ruminant. 5. The activities of lactase and maltase diminished with age. Alkaline phosphatase and aminopeptidase N activities remain constant. Sucrase activity cannot be detected in lambs of any age.     

Activity of digestive enzymes and distribution of the trematode Bunodera luciopercae (Müller) in the intestine of juvenile perch infected with plerocercoids of Triaenophorus nodulosus (Pallas)

It is revealed that the infection of Triaenophorus nodulosus (Pallas) with plerocercoids affects both the activity of digestive hydrolases and the localization of trematodes in the intestine of juvenile perch. Infected fish exhibit a higher proportion of Bunodera luciopercae (Müller) marites in the posterior intestinal segment compared to noninfected specimens. Moreover, in young fish with cestode-induced liver damage, the activities of digestive hydrolases decreases, particularly in the anterior segment of the digestive tract.     

Regional variability in circadian rhythmicity of intestinal digestive-absorptive functions.

The circadian rhythms of sucrase, maltase, isomaltase, trehalase, lactase, gamma-glutamyltransferase, leucylnaphthylamide hydrolyzing activity, alkaline phosphatase and monosaccharide transport were assessed in each fifth of the small intestine of the rat in order to determine if an entire enzyme or transport system population responded in a similar manner or if there were regional differences. Animals were maintained under a light-dark cycle and fed from 1400-1800, EST for 7 days. Functional activities were assessed every 4 h for 24 h, inclusively. Quantitative, and in a few instances, qualitative differences in different areas of the intestine were found for all functions. There were portions of the lactase and alkaline phosphatase populations which displayed no rhythmicity in activity. When rhythmicity was observed there were differences in the activity patterns along the intestine for all functions. Thus, the rhythm patterns obtained from homogenates of the entire small intestine are a composite of the patterns in regions of high average activity. Also, there appears to be a reasonable amount of local control of the various functions.