Intestinal absorption and gastro-intestinal digestion of protein in the young rat during the normal and cortisone-induced post-closure period

Prophylactic role for complementary and alternative medicine in perinatal programming of adult health

BACKGROUND

The health status of an individual in adulthood is proposed to be determined by events occurring in the prenatal and early postnatal period. A common early life event proven to have long lasting effects on the developing fetus is stress, including pain. Exposure of fetal and neonatal infants to repetitive psychological (e.g., maternal stress) or physiological (e.g., pain, infection, and noise) stress during this period is proposed to alter mechanisms involved in the regulation of stress, immunological maturation, pain perception, and cognition. Such changes, which persist into adulthood, may occur via alterations in the development of the hypothalamic-pituitary-adrenal (HPA) axis. This process is typically referred to as 'perinatal programming'. Ontogenic alterations in the development of the HPA-axis have been related to a number of adult pathologies such as cardiovascular disease, type 2 diabetes, asthma, as well as psychopathologies such as anxiety and depression.

OBJECTIVE

In this review, the effectiveness of complementary and alternative medicine (CAM), such as music, dietary supplements, massage and aromatherapy, in reducing perinatal stress in mothers and infants is examined. An emphasis is placed on these therapies as preventative measures which may be of value to individuals at risk of developing disease profiles associated with the consequences of adverse perinatal programming. The widening interest in perinatal programming and CAM suggests the potential for CAM to become a valuable tool in offsetting negative adult health outcomes resulting from perinatal programming associated with adverse gestational early life environments.

Nutritional approach to restore impaired intestinal barrier function and growth after neonatal stress in rats

OBJECTIVES

Psychological stress during the neonatal period results in intestinal barrier dysfunction and growth alterations later in life. We aimed to restore impaired barrier function and growth rate by a nutritional intervention.

METHODS

Male rat pups (n = 84) were assigned to 1 of 2 rearing conditions from postnatal day (PND) 2 to PND14: S, separated 3 h/d from their mothers, or H, 15 min/d handled controls. From PND15 to PND35, rats received a control diet or a similar diet adapted to contain arachidonic and docosahexaenoic acids, galacto- and fructo-oligosaccharides and Lactobacillus paracasei NCC2461.

RESULTS

Maternal separation had only a minor impact on the measured gut barrier parameters at PND15, whereas it severely affected them at PND35. At this age, intestinal permeability to macromolecules was higher, mucin content in small intestinal tissues was lower and microbiota composition was altered in S compared with H animals. Feeding the adapted diet normalized the intestinal permeability, although it did not restore intestinal mucin content or microbiota. In addition, the adapted diet improved the growth rate recovery of the S animals after weaning and resulted in increased villus length in small intestine.

CONCLUSION

Our results suggest that an adapted diet containing specific long-chain polyunsaturated fatty acids, prebiotics and probiotics can revert the negative imprinting of neonatal stress on both intestinal barrier function and growth.

Effect of age on the gastrointestinal absorption of acyclovir in rats

Drug elimination from the body after intravenous administration of acyclovir (20 mg kg-1) was delayed in 1-week-old rats but the pharmacokinetic data for 2.5-week-old rats were the same as those for 8-week-old rats. The areas under the plasma concentration-time curves at 0-infinity h (AUC) after oral administration of acyclovir (20 mg kg-1) decreased with increasing age. The absolute bioavailabilities for 1-, 2.5-, 3- and 8-week-old rats were 77.59, 51.52, 14.61 and 7.30%, respectively. The gastrointestinal absorption of poorly absorbed acyclovir was good for rats younger than 2.5 weeks but dropped abruptly between 2.5 and 3 weeks of age. The intestinal membrane permeability of acyclovir was studied using the everted sac method. The rate of transfer of an initial concentration of 10 microM acyclovir from the mucosal to the serosal side was constant until 60 min in rats of different ages while the rate in 2.5-week-old rats was significantly greater than that in 3-, 4- and 8-week-old rats. Abrupt in-vivo and in-vitro changes were observed in the experimental results between 2.5- and 3-week-old rats; this period coincided with the weaning period of the rat. The membrane transport mechanism of acyclovir in 2.5- and 8-week-old rats was also studied. Cumulative transferred amounts of acyclovir were linear (r = 0.99) over the range 5 microM-1 mM and dose-independent. The influence of metabolic inhibitors (sodium azide, 2,4-dinitrophenol, ouabain), purine and pyrimidine analogues (2-deoxyguanosine, guanine, adenine, uridine) and temperature on the permeation of acyclovir was studied. The permeation of acyclovir was inhibited only by 2-deoxyguanosine and guanine in 2.5-week-old rats. These results suggest that throughout the maturation period, the gastrointestinal absorption mechanism of acyclovir is predominantly via passive diffusion with little or no active or facilitated transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of undernutrition and hormone treatments on the absorption of proteins in suckling rat intestine

The absorption of 125I-labeled BSA and gamma-globulin was significantly (P less than 0.01) elevated in UN pups compared to the controls. Administration of pharmacological doses of cortisone, thyroxine, and insulin markedly (P less than 0.001) reduced the absorption of BSA and gamma-globulin in UN pups. There was no significant difference in the binding of 125I-labeled BSA and gamma-globulin to microvillus membrane in the control and experimental animals. However, the degradation of labeled BSA and gamma-globulin by luminal content was considerably higher (55-70%) in controls compared to UN pups. This suggested that observed increase in the absorption of proteins in nutritionally deprived pups was unrelated to their binding to the microvillus surface but presumably it is a consequence of reduced luminal degradation together with delayed maturational development as suggested by the pattern of brush border enzymes in the UN intestinal tissue.

Changes in the pattern of intercellular transfer of lucifer yellow between villus epithelial cells during postnatal development

We demonstrate the pattern of intercellular transfer of Lucifer yellow between villus epithelial cells during postnatal development. Epithelial cells in all villi from newborn mice demonstrate high dye transfer efficiency. The efficiency of dye transfer decreases with the age of the mouse and with villus size, until in adult mice, dye transfer is observed only in what are presumably newly forming villi. We suggest that the development of an osmolality gradient in taller villi, a result of sodium pumps and a countercurrent multiplier, may be responsible for the changes in the pattern of dye transfer observed.

The effects of steroids upon the gastrointestinal tract

The steroid hormones and bile acids are important to digestive tract structure and function. Glucocorticoids administered during pregnancy have been shown to induce cleft palate in the offspring in several species. Postnatally, a significant rise in corticosterone during week 3 in the rat coincides with profound morphological and biochemical changes in the small intestine toward the adult state. Exogenous glucocorticoids given suckling rats leads to precocious development of these changes. In the adult, glucocorticoids increase brush border enzyme levels, while adrenal insufficiency decreases mucosal weight, enzyme activity, and absorptive functions. Water and sodium absorption and potassium excretion are enhanced in both small and large intestine. The jejunum, through its sense of food, provides the entraining signal that governs corticosterone rhythm. In the stomach, high doses of glucocorticoids inhibit prostaglandin biosynthesis, thereby inhibiting the gastric alkaline response and producing severe gastric lesions. However, in man, peptic ulcer disease is not clearly associated with glucocorticoid therapy. Exacerbation of subclinical intestinal infections and perforative lesions have been observed in both animals and man given glucocorticoids. The female sex hormone estrogen, when given to rats, stimulates intestinal enzyme levels and facilitates absorption. Progesterone inhibits both circular and longitudinal smooth muscle contractile activity. Virtually the entire pool of bile acids is found in the enterohepatic circulation. The dihydroxy secondary bile acids, regardless of their conjugation states, are physiologically and morphologically more damaging to mucosal cell membranes than are the trihydroxy primary bile acids.

Development of phospholipase A2 and lysophosphatidylcholine metabolising enzyme activities in the neonatal rat intestine

We have studied the development of phospholipase A2 (PLA2) and lysophosphatidylcholine (lysoPC)-metabolising enzyme activities in the neonatal rat intestine and its relation to the intestinal permeability of macromolecules. The permeability was determined by feeding young rats a mixture of bovine serum albumin, bovine immunoglobulin G and fluorescein-isothiocyanate-conjugated dextran 70,000, and analysing the serum concentrations after six hours. The animals were then killed and the intestinal mucosa was homogenised and assessed for PLA2 and lysoPC-metabolising enzyme activities. The intestine was 'open' to the macromolecules in 14 day old animals, but 'closed' in 22 and 32 day old animals and in 14 day old rats treated with cortisone acetate on day 10, 11, and 12 postpartum. The activity of PLA2 (at pH 6 and 2 mM Ca2+) was higher in 32, 22, and cortisone treated 14 day old animals, than in untreated, 14 day old animals. Incubation of 14C-acyl-lysoPC with mucosa from 14 day old rats did not change the radioactivity pattern as shown by thin layer chromatography, whereas after incubation with mucosa from 22 or 32 day old animals all the radiolabel was found in free 14C-fatty acid and in 14C-phosphatidylcholine. These findings indicate that mucosal PLA2 activity increases during intestinal maturation and that the mucosa acquires the ability to acylate and deacylate lysoPC when it is 'closed' to macromolecules.

Studies on L-arginase in developing rat small intestine, brain, and kidney. I. Ontogenic evolution of arginase isoenzymes

The adult patterns of arginase isoenzymes in rat intestine, kidney, and brain are nearly identical and consist of two forms, cationic A1 and anionic A4. In this paper, the organ-specific maturation of the enzyme equipment in these tissues is reported. The activity of arginase in all tissues studied could be detected on the 13th to 16th days of gestation. In fetal intestine and kidney the arginase activity is low, and persists up to the weaning time when the rapid, 10-fold rise of the enzyme activity occurs. However, the adult pattern of arginase isoenzymes in these tissues is accomplished in different ways. In the intestine, arginase A1 appears in fetal life and is the only form of the enzyme till the 19th to 21st days of postnatal life when the second form of arginase, A4, appears and rapidly accumulates, being exclusively responsible for the rise of the total enzyme activity at the time of weaning. In kidney, arginase A1 alone is present in the early fetal period. Arginase A4 appears 3-4 days before birth and its activity persists unchanged within the first 2 weeks of postnatal life. The intensive rise in total specific activity of kidney arginase at weaning is due to the accumulation of preexisting arginase A4. In brain, the adult pattern of arginase isoenzymes is achieved earlier than in other tissues. Both forms, A1 and A4, occur on Days 13-14 of gestation.

Pre- and postnatal development of differentiated functions in rat intestinal epithelial cells

A panel of monoclonal antibodies to intestinal cell surface components has been used to compare the expression of differentiation-specific antigens in the epithelial cells of fetal, suckling, and adult rat small intestine. Indirect immunofluorescence staining, and immunopurification of detergent-solubilized membrane proteins, followed by single- and two-dimensional slab gel electrophoretic analysis, have demonstrated that fetal intestinal cells (at day 21 of gestation) express most differentiation-specific markers typical of adult absorptive villus cells. A marked heterogeneity in antigen expression was observed among different villus cell populations in suckling rat intestine, and three cell surface components were identified which are exclusively present during this period of intestinal development. Striking changes in the patterns of antigen expression in crypt and villus cells, and variations in the apparent isoelectric points for most luminal membrane components, were associated with the maturation of the intestinal mucosa at weaning. These changes could not be prematurely induced by cortisone injection in newborn rats, suggesting that factors other than glucocorticoids are responsible for the postnatal development of the intestinal epithelium. These results suggest that basic differences in biological properties and regulatory mechanisms exist among intestinal epithelial cells at different stages of pre- and postnatal maturation.

Whole population cell kinetics and postnatal development of the mouse intestinal epithelium

Measurements of whole population cell kinetics of mouse intestinal epithelium during postnatal development are reported. Swiss albino mice aged 1, 2, 3, 4, 6, 8, 10, 12, 16, 19, 24, and 28 weeks were studied. Isolated epithelial preparations of jejunum and colon were used. Most kinetic parameters studied either increased or decreased with age to reach a steady level sometime after weaning. For example, before weaning about 30% of crypts were observed to be branching, while after weaning, the population of crypts that were branching decreased to adult levels of 5-10% in jejunum and 1-2% in colon. Thus, there was very active crypt formation before weaning, which likely continued into adult life but at a lower level. Villus formation appeared to be occurring in animals before weaning (i.e., 1-3 weeks), while it stopped with weaning, and thus the mean villus height increased to a plateau, which was constant with age after 4 weeks. In contrast, the mean villus width increased steadily with age. As the width of villi increased with age, the number of crypts associated with a villus also increased (presumably as a result of net crypt production in the adult). These measurements and many others (proportion of cells in S phase, number of cells/cm2, number of cells/villus, number of cells/crypt, etc.) are described.

Influence of glucocorticoids on prenatal development of the gut and pancreas in rats

The effect of chronic administration of hydrocortisone during pregnancy on growth and maturation of the foetal gut and pancreas was investigated. Groups of 10- to 11-day pregnant rats were injected with saline or hydrocortisone (50 mg/kg) once a day for 10 days. The pancreas, antrum, and small intestine of newborns (8-10 h after birth) were analysed for various determinants of growth and maturation. The small-intestinal weight and DNA, RNA, and protein were significantly higher in newborns from hydrocortisone-treated animals than those of saline-treated controls. Hydrocortisone treatment resulted in an induction of sucrase and significantly stimulated total lactase activity. After the steroid treatment during pregnancy, the weight of the pancreas and its DNA content in newborns were also significantly elevated when compared with those from saline-treated controls. However, neither pancreatic RNA nor protein content differed significantly between the groups. Antral gastrin content in newborns from hydrocortisone-treated mothers was significantly higher than that from saline-treated controls. Pancreatic gastrin content in newborns was slightly but not significantly reduced after the steroid administration to mothers. It is concluded that glucocorticoids induce growth and maturation of foetal gut and pancreas.

Restricted mobility and endocytosis of anionic sites on newborn rat jejunal brush border membranes

The distribution and mobility of anionic sites on the microvillous surface of newborn rat jejunal absorptive cells were studied using polycationic ferritin (PCF) as a visual probe and were compared with anionic sites previously described for adult jejunum. Segments from 5- to 26-day-old rats were incubated in PCF for 5 minutes either before or after fixation for electron microscopy. From days 5 to 20, anionic sites were distributed diffusely along the lengths of the microvilli and did not show random translational mobility. In contrast, microvilli examined from animals at weaning (2l to 26 days) resembled those from adults in which most binding sites were capable of lateral mobility and were induced by PCF to culster into discrete patches. The diffuse pattern was altered by cortisone administration, paralleling a premature reduction in the endocytic apparatus of the cell. The difference in mobility of anionic sites with age coincides with differences in absorptive function. Evidence is presented showing that in the neonate binding of PCF to the microvilli was followed with time by endocytosis into an apical system of tubules for intracellular transport, incorporation into coated vesicles, and release through the lateral cell surface. The results suggest that endocytosis is accomplished by a mechanism that includes a directionally controlled movement for the selective internalization of PCF binding sites from the membranes of the microvilli to those of the tubular cytoplasmic channels.

Immunoglobulin absorption in calf neonates with special considerations of stress

The concept that hyperadrenalemia resulting from stress may suppress colostral immunoglobulin absorption or terminate intestinal permeability in the bovine neonate has not been substantiated by objective research. Experiments with exogenous corticosteroids or induction of endogenous secretion of the adrenals have not demonstrated the same effect as in rodents where precocious maturation of intestinal epithelium terminates macromolecular protein absorption. Evidence is given that certain prepartum stressors on the dam may influence colostral immunoglobulin absorption in the calf. High environmental temperature influences colostral immunoglobulin absorption.

Development of intestinal brush border membrane proteins in the rat

1. The proteins of the intestinal microvillus membrane have been studied during post-natal development in the rat (days 12--37). 2. In suckling animals (up to age 20 days), the majority of alkaline phosphatase, glucoamylase and lactase activities in the distal half of the intestine were located in the supernatant fraction (100000 X g, 60 min). These enzymes were attached to the membrane from the proximal intestine at all ages. 3. Alkaline phosphatase, maltase and lactase activities in the supernatant fractions chromatographed in Sephadex G-200 in positions similar to the corresponding membrane enzyme. Corresponding activities for lysosomal counter-parts of maltase and lactase present in the supernatant fraction chromatographed differently. Moreover, pH optimum of the soluble enzymes was 9.2 for phosphatase and 5.5--6.0 for glycoamylase and lactase. The soluble lactase and alkaline phosphatase were inhibited minimally by p-chloromercuribenzoate, and sodium fluoride respectively. L-Phenylalanine (20 mM) did inhibit the soluble phosphatase by 90%. Thus, the soluble enzymes are not mainly of the lysosomal origin, but have characteristics of membrane-bound enzymes. 4. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate revealed 18 protein bands which were present in adult membranes. Two other proteins were unique for membranes of distal intestine in suckling rats. The proteins corresponding to known enzyme activity changed as expected with age (e.g. sucrase, maltase increased, lactase decreased). Most of the other proteins were also altered in amount during development. Thus, the changes in the microvillus membrane during development in the rat are not limited to specific enzymes.

The effects of corticosterone and cortisone on the uptake of polyvinyl pyrrolidone and the transmission of immunoglobulin G by the small intestine in young rats

1. The distribution of polyvinyl pyrrolidone along the intestinal lumen and in the intestinal wall, following oral administration to normal and corticosterone treated rats, was found to be extremely variable. Valid comparisons between the two groups of animals could not be made using this technique. 2. Three, 4 and 5 days after corticosterone treatment there was no significant change in the uptake of 125I-labelled polyvinyl pyrrolidone from standard doses injected into ligated segments of the distal small intestine; nor did the treatment induce precocious replacement of the absorptive cells in this region. Cortisone induced precocious cell replacement, a process which took up to 4 days to complete, and also led to a marked reduction in the uptake of 125I-labelled polyvinyl pyrrolidone from ligated segments of the distal intestine. 3. Three days after treatment with corticosterone (5 mg I.P. at 12 days) there was a marked reduction of labelled immunoglobulin G transport into the blood. Four and 5 days after treatment there was some recovery of the immunoglobulin G transport function. Three days after treatment with cortisone (5 mg I.P. at 12 days) there was closure of the gut to labelled immunoglobulin G. 4. The relevance of these results to antibody transmission and the termination of immunoglobulin transport is discussed.

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.

The transmission of -125-I-labelled immunoglobulin G by proximal and distal regions of the small intestine of 16-day-old rats

1. Standard doses of -125-I-labelled rat IgG were injected into the intestinal lumen of rats aged 16 days, and their sera were sampled 2 and 3 hr later. High concentration quotients were obtained after injection into the proximal small intestime, whereas very little immunoglobulin was transmitted from doses injected into the terminal 20 cm of the small intestine. 2. The villi of the terminal 18--20 cm of the small intestine of 16-day-old rats, the region from which very little transmission of IgG occurred, were lined by tall columnar absorptive cells with very larg supra-nuclear vacuoles. The extent of the terminal intestine, in which this cell type predominated in the absorptive epithelium, varied with age. The importance of defining the precise location of the region of the intestine under examination is stressed. 3. The experimental results and the histological observations are discussed in relation to (a) the results which have been obtained using PVP, which is unsuitable as an indicator of immunoglobulin transport in the rat and (b) the histological composition of the absorptive epithelium and the maturation changes which affect the epithelium between 18 and 21 days.

Soluble neutral and acid maltases in the suckling-rat intestine. The effect of cortisol and development

The 100000g supernatants from 13-day-old suckling-rat intestinal homogenates contained 43.5% of the total intestinal maltase activity, compared with 7.1% in weaned adult rats aged 40 days. The soluble maltase activity was separated on Sepharose 4B into two quantitatively equal fractions at pH6.0, one containing a maltase with a neutral pH optimum and the other a maltase with an acid pH optimum. The neutral maltase was shown to be a maltase-glucoamylase identical with membrane-bound maltase-glucoamylase in molecular weight, heat-sensitivity, substrate specificity, K(m) for maltose and K(i) for Tris. The soluble enzyme was induced by cortisol, but the ratio of the soluble to bound enzyme fell during induction. Solubility of the neutral maltase was not accounted for by the action of endogenous proteinases under the preparative conditions used. It is postulated that the soluble neutral maltase is a membrane-dissociated form of the bound enzyme and that the relationship between these two forms is modulated by cortisol. The acid maltase generally resembled acid maltase of liver, muscle and kidney. It was shown to be a maltase-glucoamylase with optimal activity at pH3.0, and molecular weight of 136000 by density-gradient centrifugation. At pH3.0 its K(m) for maltose was 1.5mm. It was inhibited by turanose (K(i)=7.5mm) and Tris (K(i)=5.5mm) but not by p-chloromercuribenzoate or EDTA. Some 55% of its activity was destroyed by heating at 50 degrees C for 10min. The acid maltase closely resembled beta-glucuronidase and acid beta-galactosidase in its distribution in the intestine, response to tissue homogenization in various media, and decrease in activity with cortisol treatment and weaning, indicating that it was a typical lysosomal enzyme concentrated in the ileum.

Isolation of microvillus plasma membranes from suckling-rat intestine. The influence of premature induction of digestive enzymes by injection of cortisol acetate

1. Cortisone administration to suckling rats leads prematurely to induction of enzymes of the intestinal microvillus plasma membrane and lengthening of the intestinal microvilli. To investigate the membrane changes that might be involved, a method for the isolation of a fraction enriched with microvillus plasma membrane was developed in suckling rats. Plasma-membrane fractions were compared from 13-day-old control rats and from 13-day-old rats given cortisol acetate by subcutaneous injection for 3 days. 2. After cortisol injection, the activity of maltase, trehalase, sucrase and leucyl beta-naphthylamidase increased markedly, and to the same extent, in intestinal homogenates and plasma-membrane preparations. Purification, and recovery of five marker enzymes with respect to homogenate activity, and recovery of protein, were similar for both membrane preparations, particularly after correction for non-membrane activity, which was high in suckling rats and affected by cortisol. 3. In material released from the plasma membrane by digestion with papain, maltase protein was increased after cortisol injection at least as much as maltase activity. Sucrase activity increased at least 200-fold, and this increase was associated with the appearance of a new sucrase band on polyacrylamide-gel electrophoresis. 4. Sodium dodecyl sulphate electrophoresis of plasma-membrane proteins revealed at least four additional macromolecules after cortisol injection. Concurrently several proteins disappeared from the plasma membrane. The added proteins appeared in the main to be removed from the plasma membrane by papain, whereas the deleted proteins were in the papain-resistant fraction. 5. Enzymic stimulation induced by cortisol acetate in the suckling-rat plasma membrane therefore appears to involve the addition of new proteins, rather than activation of proteins in situ. Deletion of proteins from the membrane during induction of hydrolytic enzymes may reflect other phenomena such as protein reorganization associated with the change in microvillus shape.