Hepatic metabolism of orally administered prostaglandin F2 alpha in suckling and weanling rats

Suckling (12- to 14-day-old) and weanling (30-day-old) rats were sacrificed 2 h after oral administration of 3H-labeled prostaglandin F2 alpha. Although radioactivity recovered from the stomach and small intestine (including contents) was slightly higher in sucklings (28.3 +/- 3.7%; n = 10) than in weanling rats (21.3 +/- 5.3%; n = 7), the liver of sucklings contained significantly higher amounts of counts (11.0 +/- 1.1 vs. 3.3 +/- 0.5%). Combined column and thin-layer chromatography of liver extracts showed more authentic prostaglandin F2 alpha in sucklings (11.0 +/- 0.5% of the liver counts) than in weanlings (7.0 +/- 1.1%). The liver of suckling rats contained a higher percentage of more polar metabolites (43.3 +/- 1.6 vs. 34.3 +/- 3.0%). These studies demonstrate differences in processing of oral prostaglandin F2 alpha in the early postnatal period.     

In vitro intestinal processing of prostaglandin F2 alpha in rats: developmental aspects

Cytoprotective prostaglandins (PGs) such as PGF2 alpha are present in milk and can be absorbed intact from the gastrointestinal tract. Developmental differences in gastrointestinal PG metabolism in vivo have been previously reported. To evaluate the role of small intestinal tissue, detailed analysis of PG processing in vitro of small intestinal segments of suckling and weanling rats using everted sacs was performed. Sacs were incubated in Krebs-Ringer bicarbonate buffer, pH 7.4, at 37 degrees C. Bathing mucosal fluid contained [3H]PGF2 alpha. Proximal and middle intestinal segment everted sacs of suckling rats exhibited greater transfer of radioactivity in comparison with those of weanling rats. Whereas in suckling rats transfer of radioactivity decreased from proximal to distal regions of the intestine, no segmental differences were seen in weanlings. Maturational differences were also present in the capacity for PG catabolism. Suckling rat everted sacs had a greater proportion of radioactivity present as intact, unmetabolized PGF2 alpha present in sac tissue and serosal fluid in all intestinal segments in comparison with those of weanling rats. Weanling everted sacs contained greater amounts of less polar metabolites. These results indicate that there are quantitative and qualitative age-related differences in transfer and processing of exogenous PGF2 alpha in small intestinal tissue of developing rats.     

Hyperbilirubinaemia in neonatal rats after oxytocin or prostaglandin F2 alpha treatment of pregnant rats

Serum bilirubin concentrations were investigated in neonatal rats. High concentrations were found on day 1 falling to adult values by day 4. Oxytocin (500 IU/kg) given subcutaneously to the dams on day 22 of pregnancy increased bilirubin concentrations in neonatal rats. This dose of oxytocin shortened gestational length but increased the neonatal death rate. Oxytocin (500 IU/kg) also increased uterine contractions on day 22 of pregnancy, measured using intrauterine balloons inserted on day 19 of pregnancy. Rats delivered by Caesarian section at the same gestational age as the oxytocin-treated group did not exhibit hyperbilirubinaemia. Prostaglandin F2 alpha (300 micrograms/kg) administered intramuscularly on day 20 of pregnancy was found to advance parturition and produced a small rise in serum bilirubin concentrations in neonatal rats. The rat could serve as a model for investigating the mechanisms of neonatal hyperbilirubinaemia which has been suggested to occur after the use of oxytocin or prostaglandins in the human.     

Development of luminal protein digestion in suckling and weanling rats

Because previous measurements of early postnatal, small intestinal fluid, proteolytic activity in man and animals have been contradictory, we characterized the development of luminal protein digestion using a sensitive assay in which iodinated bovine casein was incubated in vitro at 37 degrees C with luminal fluid flushed from the stomach and small intestine of 12-day-old suckling and 31-day-old weanling rats, followed by measurement of radioactivity in trichloroacetic acid-soluble material. Gastric proteolysis at pH 3.2 in the weanling rat was approximately 50-fold greater than that in the suckling rat. Analysis of stomach fluid acid-soluble casein degradation products of weanling rats by chromatography on G-50 Sephadex in the presence of sodium dodecyl sulfate revealed three peaks of radioactivity comprising 65, 18 and 12% of the total product in order of elution. In the jejunum at neutral pH, the proteolytic capacity of the weanling rat was approximately five times that of the suckling rat; such differences were more pronounced in the ileum, however, in which protein hydrolysis of weanling rats was 30-fold higher than that in the suckling rat. In the suckling rat, small intestine proteolytic activity was greater in the jejunum than in the ileum, but in the weanling rat greater protein hydrolysis was present in the ileum. Gel filtration analysis of reaction products in both intestinal segments and at both ages demonstrated two peaks, which constituted 60-70 and 15-23% of the acid-soluble material in order of elution.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of short-term food deprivation on luminal protein digestion in suckling and weanling rats

Although previous studies have described the effects of long-term undernutrition on the process of protein digestion, little data exist regarding the impact of short-term food deprivation on digestive processes. To evaluate the effect of short-term food deprivation on luminal proteolytic activity in the rat, we incubated [125I]bovine casein in vitro at 37 degrees C with fluid flushed from the lumen of stomach and small intestine of 12-day-old suckling and 31-day-old weanling rats that were either fed or food deprived for 12 h/100 g body weight (3 h for sucklings, 12 h for weanlings), followed by measurement of radioactivity in trichloroacetic acid soluble material. Assays were performed at pH 3.2 for stomach and 7.4 for small intestine. In the suckling, gastric luminal proteolytic activity was minimal in both fed and food-deprived animals; jejunal and midjejunal proteolysis was not significantly affected by food deprivation, but the hydrolytic capacity of fluid from the ileum was reduced to 20% of that of fed animals. In the weanling, food deprivation increased gastric proteolytic activity two- to threefold but decreased proteolysis in jejunum and midjejunum. Time-course studies revealed that these effects were further accentuated by food deprivation for 24 h/100 g body weight in both age groups. It is concluded that short-term food deprivation may affect luminal proteolytic capacity and that individual segments of the developing rat gastrointestinal tract respond differently to food deprivation. Presumably, direct and indirect effects of digesta may contribute to these differences.     

F2alpha prostaglandin levels in mothers and infants of different gestational periods

53 mother-neonate couples, of different gestational ages, were studied for PGF2alpha levels in the mother's blood at the beginning of the first stage of labor and in the umbilical cord blood. PGF2alpha levels were found to be increased in all neonates compared to their mothers and in the blood of the mothers of prematures compared to the mothers of the post-mature babies. No correlation could be found between the gestational age of the neonate and the umbilical cord levels of PGF2alpha.     

Isolated pancreatic acini from suckling and weanling rats: changes in amino acid incorporation and carbachol-stimulated amylase secretion with age

To characterize the changes in pancreatic function during postnatal development, isolated pancreatic acini were prepared from rats aged 8-9, 12-14 and 20 days and from adult rats. Isolated acini maintained a normal microscopic appearance and viability as judged by exclusion of trypan blue and linear incorporation of tritiated leucine into total protein. The rate of incorporation in 8-day-old acini was 20% of that observed in adult rats. Significant dose-dependent increases in amylase release in response to carbachol were observed in all age groups; stimulated amylase secretion was significantly less in the 8- to 9- and 12- to 14-day-old animals than in the 20-day-old and adult rats. These data indicate that viable isolated pancreatic acini can be prepared from suckling rats and that these acini exhibit an altered in vitro responsiveness to carbachol. This preparation should therefore be a useful model for in vitro studies of the development of pancreatic function.     

Urinary excretion of prostaglandin E and F 2 alpha in healthy newborn infants and in infants with hyaline membrane disease

Urinary PGE and PGF 2 alpha excretion was estimated in 11 healthy full-term (mean birth weight, 3327 g; mean gestational age, 39.2 weeks). 15 healthy preterm (mean birth weight, 1722 g; mean gestational age, 32.1 weeks) and in 9 preterm infants suffering from hyaline membrane disease (HMD) (mean birth weight: 1454 g, mean gestational age: 31 weeks). Measurements were carried out on the 1st, 3rd and 5th days of life by radioimmunoassay, using Clinical Assays Inc. RIA kits. Urinary PGE excretion on the first day of life was 3.76 +/- 0.41 ng/day, 2.43 +/- 0.65 ng/day and 1.19 +/- 0.27 ng/day for healthy full-term, healthy premature and premature infants with HMD, respectively. The differences were significant at the level of p less than 0.05. With advancing postnatal age urinary PGE excretion markedly increased in each group (p less than 0.05). Urinary PGF 2 alpha excretion on the first day was 10.8 +/- 2.0 ng/day in full-term, 6.6 +/- 2.2 ng/day in healthy premature and 4.35 +/- 1.9 ng/day in premature infants with HMD. Then an inconsistent rise could be observed without statistically significant difference between the individual groups of various postnatal age and between the different groups of the same postnatal age. The decreased renal PGE production is suggested to be involved in the pathomechanism of HMD.     

Enterally but not parenterally administered Phaseolus vulgaris lectin induces growth and precocious maturation of the gut in suckling rats

BACKGROUND: The lectin, phytohemagglutinin (PHA) has been shown to induce growth and functional maturation of the gastrointestinal (GI) tract in suckling rats. Objectives: To investigate the effect of the administration route, and whether enteral exposure to PHA was necessary to induce functional maturation. METHODS: Fourteen-day-old rats were daily administered PHA via orogastric feeding (0.05 mg PHA/g BW) or via subcutaneous injection (0.05 or 0.005 mg PHA/g BW) for 3 days, while the controls received saline orogastrically. At 17 days of age, organ weight, intestinal and pancreatic function, and plasma corticosterone levels were analyzed. Moreover, 14-days old pups receiving a single dose of PHA, enterally or parenterally, were sacrificed after 12 h and examined for organ PHA binding using immunohistochemistry. RESULTS: Enteral PHA exposure resulted in PHA binding in the epithelial lining of the small intestine, increased gastrointestinal growth, reduced intestinal macromolecular absorption, altered the disaccharidase expression towards an adult-like pattern, and increased the pancreatic protein and trypsin contents. In contrast, parenteral PHA exposure (high dose) resulted in PHA-binding in extra-intestinal organs, increased liver and spleen weight, and decreased thymus weight. Moreover, the intestinal maltase activity increased moderately, and the transfer of BSA to blood plasma was partially reduced. Both PHA treatments led to elevated plasma corticosterone levels. CONCLUSION: These results demonstrated that enteral exposure to PHA was necessary to induce the precocious maturation of the GI tract and the pancreas, while parenteral administration affects the extra-intestinal organs. Furthermore, the enteral effects were probably not mediated via a corticosteroid dependent pathway.     

Prostaglandin metabolism in children with diabetes mellitus. I. Plasma prostaglandin E2, F2 alpha, TXB2, and serum fatty acid levels

To study prostaglandin (PG) metabolism in children with insulin-dependent diabetes mellitus, plasma levels of PGE2, PGF2 alpha, and thromboxane B2 and the composition of serum fatty acids were measured. Platelet aggregation, a risk factor in diabetic vascular complications, was also measured. The mean levels of plasma PGE2 and PGF2 alpha were high and serum dihomo-gamma-linolenic acid and arachidonic acid were low in the diabetic children. The plasma thromboxane B2 levels of the diabetic children and normal controls were not significantly different. Platelet aggregation was also increased in diabetic patients. These results suggest that the insulin deficiency and high blood sugar in diabetic children may disturb the supply of dihomo-gamma-linolenic acid from cis-linoleic acid, decreasing prostaglandin formation in series 1. Then feedback regulation may increase production of PGE2 and PGF2 alpha in series 2. Altered PG metabolism may be responsible for the occurrence and progression of vascular complications in the diabetic children.     

Effect of respiratory syncytial virus on apnea in weanling rats

Apnea is a common complication of respiratory syncytial virus (RSV) infection in young infants. The purpose of this study was to determine whether this infection affects apnea triggered by sensorineural stimulation in weanling rats. We also studied which neurotransmitters are involved in this response and whether passive prophylaxis with a specific neutralizing antibody (palivizumab) confers protection against it. Weanling rats were inoculated intranasally with RSV, adenovirus, or virus-free medium. Changes in respiratory rate and apnea in response to nerve stimulation with increasing doses of capsaicin were measured by plethysmography. Capsaicin-induced apnea was significantly longer in RSV-infected rats at postinoculation days 2 (upper airways infection) and 5 (lower airways infection), and apnea-related mortality occurred only in the RSV-infected group. Reduction in the duration of apnea was observed after selective inhibition of central gamma-aminobutyric acid (GABA) type A receptors and neurokinin type 1 receptors for substance P. Prophylactic palivizumab protected against apnea and apnea-related mortality. These results suggest that sensorineural stimulation during RSV infection is associated with the development of apnea and apnea-related death in early life, whose mechanism involves the release of GABA acting on central GABA type A receptors and substance P acting on neurokinin type 1 receptors.     

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.     

Intestinal uptake of retinol in suckling rats: characteristics and ontogeny

Uptake of retinol in the developing intestine of suckling rats (14-15 day old) and its maturation in adult rats (90 day old) was examined using intestinal everted sacs. Uptake of retinol (0.06 microM) in the jejunum of suckling and adult rats was linear for 5 min incubation and occurred at a rate of 31.20 and 6.98 pmol/g tissue/min, respectively. In both age groups, uptake of retinol (0.06 microM) was significantly higher (p less than 0.01) in the jejunum than the ileum. Uptake of retinol was significantly higher (p less than 0.01) in suckling rats as compared to adult rats both in the jejunum and the ileum. In both suckling and adult rats, the uptake of retinol in the jejunum was 1) saturable with a Vmax value of 19.78 and 6.24 nmol/g tissue/5 min and an apparent Km value of 16.20 and 8.19 microM, respectively, 2) not affected by metabolic inhibitors, and 3) partially temperature dependent (Q10 = 2.51 and 1.92, respectively). The structural analogues retinal (50 microM) and retinoic acid (50 microM) did not affect the uptake of [3H] retinol (0.06 microM) whereas unlabeled retinol (50 microM) caused significant (p less than 0.01) inhibition. No difference in retinol metabolism by intestinal tissue was observed in the two age groups. These results demonstrate that retinol uptake in suckling rats is similar to that of adult rats in being a passive carrier-mediated process. The results also suggest that a decrease in the number and/or activity and an increase in the affinity of the uptake system of retinol occurs with maturation.     

Effect of epidermal growth factor and artificial feeding in suckling rats

To evaluate the effects of epidermal growth factor (EGF) in dietary milk, a new method of delivering an artificial (EGF-deficient) formula was developed using 42 rat pups, 1-14 days of age. In a second study the effect of EGF was evaluated in suckling rats from 3-11 days of age: group 1, mother-fed; group 2, mother-fed plus daily injections of EGF (0.1 micrograms/g body weight); group 3, artificial milk fed with added EGF (62 ng/ml); and group 4, artificial milk fed without EGF. Each group consists of nine rats. In group 2 there was premature eye opening and tooth eruption and a significant reduction in body weight and weight of liver, kidney, thyroid, and thymus but an increase in length of the intestine and weights of stomach, pancreas, lung, and adrenal (p less than 0.04), when compared to group 1. Both groups 3 and 4 showed premature tooth eruption and eye opening, and their body weights and most organ weights were similar to group 2; exceptions were a smaller stomach, thyroid, thymus, lung, and adrenal, which were similar to those in group 1. In addition, intestinal length in groups 3 and 4 were similar to the mother-fed EGF-treated pups (group 2). There was no difference in intestinal length between the artificially fed pups, whether or not they received oral EGF. These findings demonstrate a new and effective technique of artificial feeding and suggest that the increase in intestinal length caused by injections of EGF (0.1 micrograms/g body weight) can also be induced by feeding an artificial milk with or without physiologic levels of EGF.     

Intestinal prostaglandin E2 expression in rats with obstructive jaundice.

AIM: How obstructive jaundice causes the intestinal barrier to be injured is still controversially discussed. In this study, we hypothesize that intestinal prostaglandin E (2), a cytoprotective factor, may be affected by the bile duct obstruction. MATERIALS AND METHODS: Four groups of Wistar-Albino rats were used: in Groups 1 and 3, the rats underwent a sham operation. In Groups 2 and 4, the common bile duct was doubly ligated. Relaparotomy was performed after one week in Groups 1 and 2, and after two weeks in Groups 3 and 4, and specimens of the jejunum, ileum and liver were obtained for intestinal PGE (2) analysis and histopathological evaluation. RESULTS: Jejunal and ileal PGE (2) levels had significantly decreased in two-week bile duct-ligated rats compared to one-week ligated rats and the sham group (p < 0.01). Tissue injury scores (Chiu score) of the ileum were significantly higher in the two-week and one-week ligated rats than in the controls (p < 0.01 and p < 0.05, respectively). The jejunal injury score was significantly higher in the two-week ligated rats compared to controls (p < 0.05). The ileal and jejunal injury scores were higher in the two-week ligated rats than in the one-week ligated rats (p < 0.01 and p < 0.05, respectively). Precirrhotic fibrosis was detected in all two-week ligated rats, but in only 7 of 10 one-week ligated rats. CONCLUSIONS: Obstructive jaundice associated with intestinal tissue injury and precirrhotic changes leads to reduced intestinal PGE (2)-levels, suggesting an adverse effect on the intestinal cytoprotective process.     

Dietary gangliosides enhance in vitro lipid uptake in weanling rats

BACKGROUND: The intestine adapts morphologically or functionally in response to environmental stimuli. Dietary lipids modify brush border membrane (BBM) permeability and nutrient transporter activities. Gangliosides (GANG) are glycolipids in human milk that are present only in low amounts in infant formula. Exogenous GANG are incorporated into cell membranes and increase their permeability. The objective of this study was to determine whether feeding a GANG-enriched diet alters in vitro intestinal lipid absorption. METHODS: Weanling rats were fed either (1) GANG-enriched diet; (2) diet enriched with polyunsaturated long-chain fatty acids; or (3) isocaloric control diet for 2 weeks, after which in vitro intestinal lipid uptake was measured. RESULTS: Feeding GANG did not alter weight gain or intestinal morphology. Enhanced uptake of stearic acid (18:0) in the ileum and stearic and linoleic acid (18:2) in the jejunum was not associated with a change in the abundance of the ileal lipid binding protein (ILBP), the intestinal fatty acid binding protein (I-FABP), or the liver fatty acid binding protein (L-FABP). CONCLUSION: We speculate that the enhanced uptake of long-chain fatty acids in weanling rats fed GANG may be caused by a modification in physical properties of the BBM.     

Carnitine and carnitine transferases in the intestinal mucosa of suckling rats

Carnitine acetyltransferase and palmitoyltransferase activity in the mucosa of the small intestine of rats rises after birth and falls at the time of weaning. The carnitine contents of the mucosa (free, acetyl-, palmitoyl- and total) decrease postnatally, reaching adult levels at the time of weaning. Orally administered 14C-carnitine is only slowly absorbed so that radioactivity is still high in plasma and organs 6 h later, whereas label given subcutaneously disappears from the plasma and tissues more rapidly. The intestinal mucosa also takes up carnitine from 14C-carnitine administered subcutaneously. It is concluded that carnitine plays an important role in the gut of suckling rats.