Newborn Pig Intestine Research Articles

Oleate Metabolism in Pig Enterocytes Is Characterized by an Increased Oxidation Rate in the Presence of a High Esterification Rate within Two Days after Birth 2

Oleate (OLE) is the principle fatty acid (FA) in mammalian colostrum, but its role in the energy supply in enterocytes after birth remains unknown. We investigated the metabolic fate of OLE in pig enterocytes at birth (d0) and after 2 d of suckling (d2). Cellular TG and phospholipids (PL) and FA composition were analyzed. Metabolic end-products of [1-14C]OLE were measured in enterocyte incubations. We characterized intestinal carnitine palmitoyltransferase 1 (CPT1), the key enzyme of mitochondrial FA oxidation. The TG content was 6.6-fold higher in enterocytes from pigs on d 2 than in those obtained on d 0, whereas the PL content did not differ. The level of OLE in TG and PL increased from 15 and 11% of total FA, respectively, in enterocytes from newborn piglets to 30 and 17%, respectively, in those from d2 pigs. The capacity for OLE utilization was 2.8-fold greater in d2 than in d0 pig enterocytes. The oxidation and esterification rates were enhanced in enterocytes from piglets on d 2 compared to those obtained on d 0, by 4- and 2.6-fold, respectively. The predominant OLE fate was the esterification pathway, representing >85% of OLE metabolized in both groups. The limited OLE oxidation observed at d 2 may result from the presence of a highly malonyl-CoA–sensitive CPT1A, because the half maximal inhibitory concentration for malonyl-CoA was 162 ± 25 nmol/L. This study highlighted the high esterification capacity for OLE in the newborn pig intestine, which may preserve this major colostrum FA for delivery to other tissues.

Ligand-Induced 5-HT3 Receptor Internalization in Enteric Neurons in Rat Ileum

Release of 5-hydroxytryptamine (5-HT) from mucosal enterochromaffin cells and activation of 5-HT(3) receptors (5-HT(3)Rs) on neurons in the gut wall is important in the response of the gut to the luminal environment. Intestinal inflammation is associated with increased levels of mucosal 5-HT. The aims of the study were to determine the following: (1) if 5-HT(3)R undergoes ligand-induced internalization in myenteric neurons, and (2) the effect of long-term increase of mucosal 5-HT on 5-HT(3)Rs. Acute effects of exogenous 5-HT or endogenous release of 5-HT by luminal glucose on cellular localization of 5-HT(3)Rs was determined by immunohistochemistry and confocal microscopy. Treatment with the serotonin re-uptake inhibitor, fluoxetine, for 6 days (20 mg/kg daily orally) was used to increase mucosal 5-HT chronically in rats. Net ileal fluid movement was measured in anesthetized rats by the weight change of a 2.5% agarose cylinder. Acute increases in 5-HT induced by exogenous or endogenous 5-HT decreased 5-HT(3)R immunoreactivity at the neuronal cell membrane by 70% and 60%, respectively. Chronic fluoxetine treatment increased mucosal levels of 5-HT and decreased membrane 5-HT(3)R immunoreactivity by 27%. Net fluid absorption was decreased by a 5-HT(3)R agonist or by luminal glucose; this was attenuated 88% and 99%, respectively, by fluoxetine treatment. Long-term increase in 5-HT in the intestinal mucosa results in increased 5-HT(3)R internalization in myenteric neurons. Chronic changes in mucosal 5-HT may alter gastrointestinal secretory and motor function via ongoing loss of receptor from neuronal membrane, causing a mismatch between luminal content and absorption.

Three-dimensional organization and functional relationships of endocytotic compartments in pig intestinal epithelial cells

The newborn pig intestine is adapted for the rapid and efficient absorption of nutrients from colostrum. In enterocytes, colostral proteins are taken up into an apical endocytotic complex of channels that transports them to target organelles or to the basal surface for release into the circulation. The apical endocytotic complex of tubules and vesicles clearly is a major intersection in the routes taken by vesicles trafficking to and from the Golgi, lysosomes, and the apical and basolateral cell surfaces.Jejunal tissues were taken from piglets suckled for up to 6 hours and prepared for electron microscopy and immunocytochemistry as previously described.

Cytochemical analysis of single villus peptidase activities in pig intestine during neonatal development.

The present work uses a new technique of whole tissue cytochemistry and automated scanning to obtain measurements of peptidase activity and surface structure in intact villi microdissected from the jejunum of newborn and 28-day-old pigs. Intact villi from 28-day-old pigs are shown by this method to contain 30% more aminopeptidase N and 400% more dipeptidylpeptidase IV activity than is found on villi taken from newborn pig intestine. Villi taken from 28-day-old pig intestine are also half as long and twice as wide at their base as those taken from newborn animals. These changes in shape take place without significantly affecting the total surface area of the villus. Increases in peptidase activities occurring during postnatal development can be further subdivided into those dependent upon induced changes in enterocyte biochemistry and those dependent upon the changing geometry of villi. Over 90% of the total increase in peptidase activities occurring during neonatal development was shown, by this analysis, to involve enterocyte reprogramming of enzyme production. The present method of whole tissue cytochemistry appears to combine successfully the ability to measure peptidase activities at the cellular level in undisrupted tissue with a facility to relate these results to the overall shape of a single villus. These and more general applications of the method now provide new ways to analyse a variety of changes taking place in intestinal structure and function in a quantitative manner.

Disaccharide uptake by brush-border membrane vesicles lacking the corresponding hydrolases

Intestinal disaccharide uptake was studied with isolated brush-border membrane vesicles lacking the corresponding hydrolase. Either 15-day-old chick intestine, lacking both trehalase and lactase, or newborn pig intestine, lacking sucrase, was used. Both animal species yielded osmotically active vesicles capable of D -glucose/Na + cotransport with a positive overshoot test. Vesicles from either origin gave quantitatively similar results in regard to both initial uptake rates and relative vesicle volumes. The nontransported analogs D -mannitol and L -glucose were used as diffusion markers. When tested with the appropriate disaccharidase-lacking vesicles, lactose, trehalose and sucrose exhibited uptake rates indistinguishable from those of D -mannitol and L -glucose. These uptakes were unaffected by the presence or absence of Na +, phlorizin and Tris. Chromatographic analysis confirmed the lack of hydrolysis of each disaccharide after prolonged incubation. The inescapable conclusion seems to be that intact disaccharides are not transported through the brush-border membrane, their uptake occurring through simple diffusion.

High interferon titer in newborn pig intestine during experimentally induced viral enteritis.

We looked for the presence of interferon in the digestive tract of newborn piglets infected with a virulent strain of transmissible gastroenteritis virus (Coronaviridae). High levels of type 1 interferon activity were found early in the disease in jejunal and ileal parts of the intestine as well as in the serum. Enterocytes appeared to be involved in the interferon synthesis. These findings raise the question of the role of interferon in the pathogenesis of viral enteritis.

Different pathways for lysine transport across neonatal pig intestine.

1. Undirectional fluxes of lysine, presented free and in the form of a dipeptide, have been measured in vitro using the small intestines of pigs taken during the first 2 weeks of post-natal life. 2. The concentration dependence of free lysine transfer to the serosal surface of new-born pig intestine (Jms) can be described as the sum of a saturable (Km 0.2 mM; Jm 3 n- mole cm-2 in-1) and a non-saturable (1.0 n-mole cm-2 min-1 mM-1) component. 3. The dipeptide isoleucyl-lysine was hydrolysed completely during transfer to the serosal surface of intestines taken at all stages of development. The concentration dependence of peptide-derived lysine transfer can be described as if it took place through a single saturable process (Km 5 mM; Jm 27 n-mole cm-2 min-1). 4. The mucosa to serosa transfer of free lysine fell to a half and that of peptide-derived lysine fell to a quarter, during the first 8 days of post-natal life. The decline in peptide-derived lysine transport correlated with changes in peptide hydrolase activity, measured in homogenates of intestinal mucosa using isoleucyl-lysine as substrate. 5. The new-born pig intestine transported lysine derived from isoleucyl-lysine twice as quickly as from lysyl-isoleucine. Lysine and isoleucine did not inhibit the transfer of isoleucine and lysine derived from isoleucyl-lysine. The transport of lysine, but not isoleucine, from isoleucyl-lysine took place more quickly than from equimolar solutions of the free amino acids. 6. It is suggested from these results that lysine and isoleucyl-lysine use different pathways when crossing the intestinal mucosa. Attempts are made to assess the probable contributions made by these pathways to the total absorption of lysine taking place during neonatal development.

Amino acid transport by small and large intestine of newborn pig.

Unidirectional fluxes of different amino acids have been determined across newborn pig small intestine and colon. The systems responsible for amino acid transport are present in the same proportion in both tissues. Colonic transport of amino acids appears to represent a transient overspill function of the small intestine.

Growth and cell replacement in the new-born pig intestine.

Both macroscopical and microscopical aspects of growth in the pig small intestine have been measured and related to the kinetics of cell turnover and changing physiological function in the period immediately following birth. The first 10 days of post-natal life was associated with an 80 % increase in length and a 30 % increase in diameter of the small intestine. The absorptive area doubled during this period of post-natal growth. Villi formed at birth were 29, 50 and 75 % longer by day 10 (proximal, mid and distal regions respectively). Maximal elongation occurred on day 6 of post-natal life. Thymidine labelling of cells showed mitosis to be confined to the crypts. Newly formed cells migrated onto the villi. The mean rate of cell appearance in a section was 0.4 cell/h. This rate remained unchanged and independent of the area of the small intestine chosen for study during the first 4 days of post-natal life. ^Examination of villus sections at different times following injection of radioactive thymidine showed considerable cell mixing to occur. Labelled cells, which never formed protein-filled vacuoles, became mixed with vacuolated and non-vacuolated, unlabelled cells. There was also a redistribution of labelled cells upon the villus. The level of radioactivity within cells did not always correspond to that predicted from their respective positions on the villus. Two alternative theories are put forward to account for these findings. The time taken for complete cell replacement is approximately 19 days. The mucosal uptake of macromolecules finally ceases and the resistance of piglets to enteric viral infections increases at about this time. It is suggested that both events are dependent on the final disappearance of cells originally present in the pig intestinal mucosa at birth.

Glucose- and phlorrhizin-protected thiol groups in pig intestinal brush-border membranes.

Purified brush borders, prepared fro newborn pig intestine, were incubated in the presence of 203Hg-labelled p-chloromercuribenzenesulphonic acid and the membrane proteins later separated by polyacrylamide-gel electrophoresis. The presence of either D-glucose or phlorrhizin, during a preliminary incubation in non-radioactive p-chloromercuribenzenesulphonic acid, increased the subsequent binding of the 203Hg-labelled compound to a protein of molecular weight 31500. This increase appeared to be specific for the low-molecular-weight protein, provided that the concentration of protecting agent used corresponded to that used to produce a biological response in the intact tissue. These results are discussed in relation to the known properties of other presumptive sugar carriers isolated from different membranes.

Calcium dependence of protein transport by the small intestine of the new-born pig.

El transporte de albumina en el intestino delgado del cerdo esta asociado con un aumento en el transporte de fluido. Ambos transportes son inhibidos por altas concentraciones de calcio. Ausencia de calcio tambien inhibe el transporte de albumina. Condiciones optimas en el transporte de albumina y fluido se obtienen usando Cl2Ca4 mM en el medio. Se deducen analogias al comparar estos resultados con resultados similares en ameba, obtenidos de la literatura.

The absorption of polyvinyl pyrrolidone by the new-born pig intestine.

1. The intestinal absorption of [(131)I]polyvinyl pyrrolidone of mean mol. wt. 160,000 (K. 60) and 40,000 (K. 30) after oral administration has been measured in unsuckled conscious pigs less than 20 hr old. Absorption was assessed by the measurement of the concentration of [(131)I]PVP in venous blood during the 6 hr after feeding and also by the distribution at the end of the experiment of [(131)I]PVP between homogenates of the alimentary tract and homogenates of the rest of the animal.2. The concentration of [(131)I]PVP in the peripheral blood after feeding was dependent upon the mol. wt. of the polymer, when comparable amounts had been absorbed from the intestine. PVP K. 60 attained higher blood concentrations than PVP K. 30 and the blood concentrations of PVP K. 60 were close to the values to be expected if all the material which had left the intestine had remained in the blood. The lower blood concentrations found when PVP K. 30 was fed were associated with the disappearance of labelled solute from the gut and were thus the consequence of the relatively rapid escape of labelled solute from the plasma after absorption had taken place.3. The ability of the intestine to absorb [(131)I]PVP K. 60 declined progressively after birth but did not terminate abruptly unless the animal was fed colostrum. In unsuckled animals the rate and extent of absorption at 3 hr was much greater than at 20 hr after birth, but some absorption was still present at least 65 hr after birth.4. The transfer of PVP K. 60 to the peripheral blood was dependent upon factors in sow colostrum, since significant absorption did not occur when PVP was fed in water or simple salt solutions.5. The factors which accelerated absorption were present in colostrum from the goat, cow and ewe as well as that from the sow; they remained in the whey, but, in contrast to the factors which accelerate absorption in the calf, were largely inactivated by boiling. Similarly, neither phosphate, lactate, pyruvate, nor lower volatile fatty acid salts, which were effective in the calf, accelerated absorption in the pig.6. The absorption of [(131)I]PVP K. 30 was found to be much less dependent upon the composition of the solvent than the absorption of [(131)I]PVP K. 60, although absorption was most rapid when PVP K. 30 was fed in colostrum.

The transport of various immune globulins by the new-born pig intestine.

El intestino delgado del cerdo recien nacido, usado in vitro, transporta immunoglobulina G (IgG) de bovino mas rapido que IgG de porcino. El transporte intestinal tanto de sodio como de fluido aumenta en presencia de IgG de bovino. Preparaciones de IgG de ovino, equino y humano son transportadas a igual velocidad que IgG de porcino. Estas proteinas no estimulan la transferencia de sodio o fluido. Esta diferencia en la velocidad de transporte entre IgG de bovino y porcino pone en duda la opinion general que sostiene que la absorcion de proteina en el intestino de cerdo es enteramente no selectiva.

Effect of poly-L-arginine on rate of bovine IgG transport by newborn pig intestine.

MOVEMENT of protein molecules within and across the plasma membranes of mammalian cells probably occurs more widely than is generally realized. Examples of protein transport that are not normally considered in the same light include the supposed movement of “carrier” proteins within the plasma membrane1, the penetration of albumin into isolated tumour cells2 and the endocytosis of proteins by the epithelium of the small intestine3. Yet the protein–membrane interactions which probably accompany the movement of protein molecules in each case are likely to have certain features in common. For example, transported protein must show some temporary affinity for constituents of the membrane, and the actual movement of protein across the membrane will cause some distortion of otherwise stable structures. The experiments described here were designed to test whether the transport of protein by the pig intestinal mucosa was in any way similar to the transport of protein into tumour cells, a system which has been used extensively to study some of the macromolecular interactions associated with protein transport2.

Interdependence of albumin and sodium transport in the foetal and new-born pig intestine.

1. Everted sacs of new-born pig intestines incubated in bicarbonate saline at 37 degrees C, transferred bovine plasma albumin across the mucosa into fluid bathing the serosa, the amount transferred increasing as the concentration of albumin in the mucosal fluid was raised from 0.5 to 16 g/100 ml.2. The rate of albumin transfer across the foetal pig intestine showed an apparent maximum, about 400 mug/g intestine/hr, 2 weeks before birth. The transfer at birth, about 200 mug/g intestine/hr, fell sharply during the next 2 days but later returned to that previously found at birth.3. When sacs were prepared from the intestines of 1 to 7-day-old pigs part of the recovered albumin was degraded. No digestion was found when the intestines of new-born or foetal pigs were used.4. The transfer of water and sodium, but not glucose, measured across the foetal and new-born pig intestine, was consistently higher when albumin was present in the mucosal fluid: the transmural potential difference was lowered by the presence of albumin. These differences disappeared during the first 2 days of life.5. Both the total and ouabain-sensitive adenosine triphosphatase (ATPase) activities of the pig intestinal epithelium fell within 24 hr of birth. There was some increase in total ATPase activity in older pigs but the ouabain-sensitive activity remained low.6. The relation between albumin and sodium transport, seen at a time when albumin is not being metabolized, suggests that the transfers are closely coupled. The movement of sodium into a mucosal cell down its own concentration gradient may provide energy for the translocation of albumin.

Effect of amino-acids on the transport of bovine immune lactoglobulin across newborn pig intestine.

THE everted small intestine of the newborn pig, formed into sacs and incubated in a preparation of dialysed bovine colostrum, transports bovine immune lactoglobulin to the serosal surface; most of the protein transport occurs across sacs made from the middle third of the intestine1. This part of the small intestine is not outstanding in its ability to transport either water, sodium or glucose, but in other mammals this is the area for maximal transport of several amino-acids2. Amino-acids can either induce or suppress endocytosis in amoebae3 and it was these two observations which suggested that amino-acids could influence protein transport in the pig intestine.