Leucylnaphthylamidase in the small intestine of the mouse: normal development and influence of cortisone and antibiotics

Hydrocortisone induces changes in gene expression and differentiation in immature human enterocytes

It is known that functional maturation of the small intestine occurring during the weaning period is facilitated by glucocorticoids (such as hydrocortisone, HC), including an increased expression of digestive hydrolases. However, the molecular mechanisms are not well understood, particularly in the human gut. Here we report a microarray analysis of HC-induced changes in gene expression in H4 cells (a well-characterized human fetal small intestinal epithelial cell line). This study identified a large number of HC-regulated genes, some involved in metabolism, cell cycle regulation, cell-cell or cell-extracellular matrix communication. HC also regulates the expression of genes important for cell maturation such as development of cell polarity, tight junction formation, and interactions with extracellular matrices. Using human small intestinal xenografts, we also show that HC can regulate the expression of genes important for intestinal epithelial cell maturation. Our dataset may serve as a useful resource for understanding and dissecting the molecular mechanisms of intestinal epithelial cell maturation.

Intestinal hormones and growth factors: effects on the small intestine

There are various hormones and growth factors which may modify the intestinal absorption of nutrients, and which might thereby be useful in a therapeutic setting, such as in persons with short bowel syndrome. In part I, we focus first on insulin-like growth factors, epidermal and transferring growth factors, thyroid hormones and glucocorticosteroids. Part II will detail the effects of glucagon-like peptide (GLP)-2 on intestinal absorption and adaptation, and the potential for an additive effect of GLP2 plus steroids.

A combination of dexamethasone and glucagon-like peptide-2 increase intestinal morphology and glucose uptake in suckling rats

OBJECTIVES

Glucagon-like peptide (GLP)-2 enhances nutrient uptake in adult animals. Glucocorticosteroids accelerate intestinal ontogeny and increase nutrient uptake in adult animals. We hypothesized that administering GLP-2 and dexamethasone (DEX) to suckling rats will enhance sugar uptake and that this effect persists into the postweaning period.

METHODS

Suckling rats were treated for 10 days with GLP-2 (0.1 microg/g/d, twice daily), DEX (0.128 microg/g/d, once daily), GLP-2 + Dex (same doses as above), or placebo. The rate of intestinal uptake of glucose and fructose in sucklings (19-21 days old) and weanlings (49 days old) was assessed using an in vitro ring technique.

RESULTS

DEX reduced body weight in weanlings, whereas GLP-2 + DEX prevented this effect. In sucklings, GLP-2 + DEX increased ileal villous height and jejunal and ileal villous width and crypt depth. In sucklings, GLP-2 + DEX increased the maximal transport rate (Vmax) for jejunal glucose uptake, whereas DEX reduced the ileal Vmax. In weanlings, GLP-2 + DEX increased jejunal villous height, whereas ileal villous width and crypt depth were reduced. DEX increased the ileal Vmax and apparent affinity constant for glucose in weanlings.

CONCLUSIONS

The combination of these hormones may be useful in stimulating glucose uptake in the developing intestine, and giving DEX to sucklings may enhance glucose uptake in later life.

Reversibility of spermine-induced intestinal maturation in the rat

In the present investigation, the reversibility of spermine-induced precocious intestinal maturation was studied. Neonatal rats received either saline or spermine (4 mumol, twice daily) solution orally on the 11th and 12th postnatal day. They were killed on the 13th, 14th, 15th, 16th, and 17th postnatal days. After the small bowel was removed, it was either divided into three equal parts or prepared for electrophoretic analysis. Histological examination, protein content measurement, and disaccharidase activity estimation were performed on each part of the intestine. Spermine administration was shown to induce structural and mucosal enzyme changes characteristic of postnatal maturation. This phenomenon, which was generally clearly observed in 13- and 14-day-old rats, then became less apparent in 15- and 16-day-old animals. Differences were noted according to the segment of intestine or the biochemical parameter analyzed. When rats were 17 days old, no significant differences generally existed between control and spermine-treated rats. If the 140- to 150-kDa proteins, isolated by electrophoresis, are assumed to represent the subunits of the sucrase-isomaltase complex, the results obtained indicate that spermine induces a modification of the concentration of this complex. When compared to values obtained in adult rats, the concentration of the complex was approximately three times higher in spermine-treated 13-day-old rats, while no differences were found in spermine-treated 14-day-old rats. Further, similar concentrations were found in control and spermine-treated rats with an age of 17 days. These results suggest that spermine-induced precocious intestinal maturation is reversible when spermine treatment is stopped.

Intestinal leucine aminopeptidase and alkaline phosphatase: genetic regulation and development in mice

Intestinal and serum leucine aminopeptidase (LAP) and alkaline phosphatase (AKP) were characterized by electrophoresis for eight inbred strains of laboratory mice. Intestinal LAP and AKP of adult mice were expressed concordantly within strains, as banded or diffuse, and concordantly for rate of migration within strains that had diffuse isozymes. All strains, except DD/S, had a single band of serum LAP and a single, diffuse zone of serum AKP. DD/S had a double band of serum LAP as well as isozymes of intestinal LAP and AKP unlike those of other strains. All strains displayed similar, neuraminidase-sensitive isozymes of intestinal LAP and of AKP prior to weaning, but after weaning there was marked sensitivity to neuraminidase only in DD/S. In interstrain crosses, banded/diffuse, migration rate, and neuraminidase sensitivity were inherited as independent autosomal traits, with indications of variable penetrance and genetic interaction.

Developmental profile of DNA synthesis and hydrolase activities in human fetal kidney

This study provides original data on human fetal kidney developing during the 13th to 18th week of gestation. The parameters evaluated were DNA synthesis and the activities of 5 hydrolases which are considered as good markers of the brush border membrane differentiation. The conclusions are that DNA synthesis decreased slightly from the 16th to 18th week. The activities of maltase, trehalase, alkaline phosphatase and leucylnapthylamidase remained nearly stable during the studied period. Only the gamma-glutamyltransferase activity decreased significantly between the 15th and 16th week, then it returned close to the 13th week value. The current results suggest that during the 13-18 week period of gestation, cell proliferation is slowed down while maturation of some enzymic activities of the brush border are not importantly modified. The present basic data might be used as reference standards by investigators in the field of human nephrogenesis.

A new variant of serum leucine aminopeptidase in the mouse: its development and possible regulation

Serum leucine aminopeptidase (LAP) isozymes were compared in four strains of inbred mice during postnatal development, adult life, and pregnancy. In pregnancy, no changes in the maternal serum LAP pattern were observed, in contrast to human studies. One strain, DD/S, differs from the other three in serum LAP. Polymorphism in serum LAP has not been previously described in the mouse. Neonatal DD/S mice exhibit a single band of serum LAP upon starch gel electrophoresis; however, between 14 and 18 days of age, two distinct bands appear, which persist throughout adult life. In the strains C57BL/6J, BALB/cJ, and DBA/2J there is a single band of activity at all stages. Crosses and backcrosses between DD/S and C57BL/6J show that the double-band variant is inherited as an autosomal recessive. The variant is independent of both the supernatant malic enzyme (Mod-1) and the intestinal LAP (Lap-1) loci, which are known to be linked on chromosome 9. The serum LAP variant is linked to an intestinal alkaline phosphatase variant. The presence of a separate structural gene is suggested by the genetic independence of the serum LAP variant from Lap-1. Also, the two serum LAP bands of DD/S are not interconverted by treatment with neuraminidase, beta-mercaptoethanol, or heat or by mixing the sera of DD/S and C57BL/6J prior to electrophoresis. The level of serum LAP activity in DD/S is approximately twice that in C57BL/6J. While these observations imply two structurally distinct proteins, the absence of any trace of the second LAP band in the heterozygote strongly suggests that the LAP variant protein is not the result of a separate structural gene. Intestinal LAP in DD/S migrates with the same electrophoretic mobility as the serum LAP variant, implying that the variant might originate in the intestine and its appearance in the serum be modulated by some factor at an unlinked locus.

Developmental pattern of glucose-6-phosphatase activity in the small intestine of the mouse fetus

The distribution of glucose-6-phosphatase (G6Pase) activity in the epithelium of the small intestine in mouse embryos (the last 4 days of gestation) was studied by electron microscope cytochemistry and by enzymatic assays. At 16 days, the lead phosphate deposited by the cytochemical reaction is localized on the rough endoplasmic reticulum (RER) and nuclear envelope of very few cells in the duodenum and jejunum. Positive cells are more frequently seen in the upper part of the developing villi. At 17 days of gestation, a tremendous burst in RER differentiation is noticed in all parts of the small intestine and concomitantly glycogen disappears. At 18 days of gestation all the principal cells of the intestinal mucosa show a well differentiated positive RER and the enzyme is also present in the smooth endoplasmic reticulum. Biochemically, G6Pase activity is detected in the proximal 2 thirds of the small intestine at 17 days of gestation and appears at 18 days in the last third. Afterwards the activity increases up until birth. These results suggest (1) that the endoplasmic reticulum differentiates very late in the intestinal mucosa of mouse embryos (2) that the differentiation with respect to G6Pase is asynchronous between the enterocytes, (3) that for a given cell all the cisternae of RER are involved in G6Pase synthesis at the same moment and (4) that the enterocytes of the duodenum differentiate sooner and faster that those of the jejunum and ileum.

Effects of cortisone and thyroxine on intestinal trehalase activity in infant mouse

Cortisone acetate (25 microgram/g b.wt/day) administration to 8-day-old suckling mice induces a premature increase of trehalase activity along the entire small intestine. On the other hand, thyroxine (1 microgram/g b.wt/day) in unable to provoke a precocious increase of trehalase activity. Trehalase appears to be the only brush border membrane disaccharidase controlled solely by glucocorticoid hormones during the postnatal maturation of the intestine.

Intestinal enzymes activities in isolated villus and crypt cells during postnatal development of the rat

A modification of Weiser's (1973) cell isolation method was used in order to study the developmental pattern of various intestinal enzyme activities in villus and crypt cells of normal rats from 5 days after birth until 8 weeks. Alkaline phosphatase and enterokinase activities were always located in the upper villus zone during postnatal development. Enterokinase activity was higher in the upper villus cells during the third week of life than after this period. Aminopeptidase activity was located in the crypt cells during the first week, its maximum activity remained in this area until the third week. At this time, sucrase activity appeared in the crypt cells, then aminopeptidase and sucrase activities rose to the villus zone during the fourth week. Amylase activity was detected along the entire crypt-villus axis 5 days after birth, reaching maximum activity in crypt cells at the end of the first week and in the upper villus cells after the fourth week. In contrast with the other enzymes studied almost all amylase activity was soluble in the youngest animals whereas at weaning most of the activity appeared in a particulate form in the villus cells. But in the crypt cells the ratio between particulate and soluble form remained unchanged until the adult stage. Various hypotheses are advanced to explain the patterns of evolution of the different enzymes.

Enzyme histochemistry as a link between biochemistry and morphology

The presented paper describes the role of enzyme histochemistry in cell biological investigations. In the first chapter a general discussion has been given about enzyme histochemistry as a connecting link between biochemistry and morphology. The methods available for determination of enzymes in a particular cell or cell compartment have been reviewed. In this respect the characteristics of enzyme histochemistry have been discussed. Furthermore, attention has been paid to the possibilities and limitations of enzyme histochemistry. In chapter two a comparison has been made between histochemically judged and biochemically determined enzyme activities. Some fundamental differences between the biochemical and the histochemical approach in cell biological investigations are dealt with. To correlate histochemically and biochemically determined enzyme activities, a description has been given of the application of histochemical methods on isolated fractions and sucrose-ficoll gradients of these fractions. Several experimental results are described concerning the question whether a relation exists between histochemically and biochemically determined activities of respectively alkaline phosphatase, glucose-6-phosphatase, 5'-nucleotidase and 3ss-hydroxysteroid dehydrogenase. From these results the conclusion could be drawn that in general a good correlation exists between histochemically judged activity per volume (area X thickness) and biochemically determined activity per gram tissue. In chapter three the role of enzymes as markers of cellular particles and as parameters of metabolic pathways is described. Histochemical methods are available for most marker enzymes. Only activities of key enzymes can be regarded as parameters of metabolic pathways. The distribution in sucrose-ficoll gradients of enzymes, regarded as markers of mitochondria, lysosomes, endoplasmic reticulum and plasma membranes has been given. The changes occur ing under different experimental conditions for a number of marker enzymes in rat liver are described. Attention has been given to the contibution of enzyme histochemistry in the study of the heterogeneity of mitochondria, the dual localization of some (lysosomal) enzymes, the complexity of the microsomal fraction, the function of the Golgi apparatus and the heterogeneity and function of plasma membranes. Based on these results and on literature findings the possible role of some marker enzymes in cell metabolism has been discussed. In chapter four problems coherent with species and sex differences in enzyme activities are described. The interpretation of histochemical and biochemical results in view of these differences is discussed. Enzymes characteristic for a given cell type -3ss-hydroxysteroid dehydrogenase in steroid producing cells, ATP-ase in liver plasma membrane surrounding the bile canaliculi - do show less variations between species and sexes than enzymes not directly involved in specialized functions...

Influence of glucocorticoids on some morphological and biochemical aspects of rat small intestinal mucosa

Glucocorticoid administration (5 mg/day per 100 g of body weight) to month-old rats elicited a reduction of maltase and alkaline phosphatase. Corticotrophic stimulation on month-old rats elicited a specific rise in maltase and alkaline phosphatase activities, total protein content remaining unchanged. Immunological, histological, radioautographical and biochemical studies have shown that these two opposing phenomena do not depend on enzyme activation, on membrane stabilisation, or on modifications of proliferative parameters of the intestinal epithelium. They appear rather to derive from the same origin, i.e. the action of glucocorticoids on the enterocyte differentiation.