Hen Colon Research Articles

Intestinal Mucosal Immunity-Mediated Modulation of the Gut Microbiome by Oral Delivery of Enterococcus faecium Against Salmonella Enteritidis Pathogenesis in a Laying Hen Model.

Enterococcus faecium (E. faecium) is a protective role that has crucial beneficial functions on intestinal homeostasis. This study aimed to investigate the effects of E. faecium on the laying performance, egg quality, host metabolism, intestinal mucosal immunity, and gut microbiota of laying hens under the Salmonella Enteritidis (S. Enteritidis) challenge. A total of 400 45-week-old laying hens were randomly divided into four treatments (CON, EF, SCON, and SEF groups) with five replicates for each group and 20 hens per replicate and fed with a basal diet or a basal diet supplemented with E. faecium (2.5 × 108 cfu/g feed). The experiment comprised two phases, consisting of the pre-salmonella challenged phase (from day 14 to day 21) and the post-salmonella challenged phase (from day 21 to day 42). At day 21 and day 22, the hens in SCON and SEF groups were orally challenged with 1.0 ml suspension of 109 cfu/ml S. Enteritidis (CVCC3377) daily, whereas the hens in CON and EF groups received the same volume of sterile PBS. Herein, our results showed that E. faecium administration significantly improved egg production and shell thickness during salmonella infection. Also, E. faecium affected host lipid metabolism parameters via downregulating the concentration of serum triglycerides, inhibited oxidative stress, and enhanced immune functions by downregulating the level of serum malondialdehyde and upregulating the level of serum immunoglobulin G. Of note, E. faecium supplementation dramatically alleviated intestinal villi structure injury and crypt atrophy, and improved intestinal mucosal barrier injuries caused by S. Enteritidis challenge. Moreover, our data revealed that E. faecium supplementation ameliorated S. Enteritidis infection-induced gut microbial dysbiosis by altering the gut microbial composition (reducing Bacteroides, Desulfovibrio, Synergistes, and Sutterella, and increasing Barnesiella, Butyricimonas, Bilophila, and Candidatus_Soleaferrea), and modulating the gut microbial function, such as cysteine and methionine metabolism, pyruvate metabolism, fatty acid metabolism, tryptophan metabolism, salmonella infection, and the PI3K-Akt signaling pathway. Taken together, E. faecium has a strong capacity to inhibit the S. Enteritidis colonization of hens. The results highlight the potential of E. faecium supplementation as a dietary supplement to combat S. Enteritidis infection in animal production and to promote food safety.

Applied Research Note: Internal organ colonization and horizontal transmission of experimental Salmonella Enteritidis and Salmonella Kentucky infection in vaccinated laying hens in indoor cage-free housing

Summary Cage-free housing of laying hens may provide opportunities for widespread environmental distribution of Salmonella contamination and horizontal transmission of infection within flocks. Salmonella Enteritidis in commercial laying flocks presents an ongoing public health concern because reproductive organ colonization in hens leads to deposition inside eggs. Many S. Enteritidis control programs include vaccination to induce protective immunity against infection. Salmonella Kentucky is common in egg production environments but has not been associated with egg contamination. This study compared the invasion of internal organs and horizontal spread of infection during the first 2 wk after experimental S. Enteritidis and S. Kentucky infection of previously vaccinated laying hens in indoor cage-free housing. Two groups of 72 hens each were housed in isolation rooms simulating commercial cage-free barns and 1/3 of the hens were orally inoculated with either S. Enteritidis (1 room) or S. Kentucky (1 room). At 6 and 12 d after inoculation, half of the hens in each room were euthanized and samples of the liver, spleen, ovary, oviduct, and intestinal tract were removed for bacteriologic culturing. Among hens inoculated with S. Enteritidis, 66.7% of the intestinal, liver, and spleen samples were positive for the pathogen at 6 d after infection, as well as 41.7% of intestines and 16.7% of livers from contact-exposed hens. Significantly (P

Salmonella Colonization of Production Hens Fed a Parietal Yeast Fraction with High Levels of Mannan and Beta-Glucan

Salmonella Colonization of Production Hens Fed a Parietal Yeast Fraction with High Levels of Mannan and Beta-Glucan

A comparative study on the colonization of Salmonella enteritidis hilA mutant and its parent strains in laying hens

BACKGROUND: Several regulatory proteins are involved in Salmonella invasion. The key regulator of SPI-1 (Salmonella pathogenicity island 1 ) is hilA, a transcriptional activator encoded on SPI-1 that regulates the expression of the SPI-1 secretion system. OBJECTIVES: Importance of hilA mutation on S. enteritidis colonization and shedding in layer hens was evaluated in a long-term experiment. METHODS: Two groups of layer hens were orally inoculated with 1010 CFU of hilA and parent strains of S. enteritidis, consequently. At days 2, 7, 14, 21 and 35 post-inoculation samples were taken from cloaca and different parts of digestive and reproduction systems of euthanized birds. RESULTS: In the birds infected with parent strain, the higher numbers of colonizing bacteria in the liver, spleen, caecum, small intestine and cloaca-vagina were observed. Fecal shedding in this group was also higher than the hilA group. However, no significant differences were observed for the colonization of bacteria in magnum, isthmus and infundibulum of both groups. Using PCR method, hilA gene was only detected in tissues of parent group hens. CONCLUSIONS: This study has shown that the hilA mutant is able to colonize in internal organs; an implication of this is the possibility that genes other than hilA, or at least other mechanisms, might be involved in the invasion of S. enteritidis to the internal organs of birds.

Toward Better Control of Salmonella Contamination by Taking Advantage of the Egg's Self‐Defense System: A Review

Egg-associated salmonellosis is a major problem for food safety. It can be caused by vertical transmission (transovarian transmission) in hens and horizontal transmission though penetration. Despite a series of physical and chemical defense mechanisms naturally found in eggs, they cannot provide complete protection for them. Environmental hygiene, bacteria vectors such as birds, rodent, flies, and beetles along with feed and water contamination are the most frequently reported causes of Salmonella colonization in hens, and finally to eggs. In addition, inappropriate egg handling will cause eggs to lose their self-protection ability, thus resulting in the survival and multiplication of Salmonella in an egg's contents, which contributes to the horizontal dissemination. The routes of Salmonella contamination were discussed, and the effectiveness and shortcomings of different decontamination methods were evaluated in this review. Various studies on egg storage indicated that the low-temperature storage without temperature fluctuation was beneficial for the control of Salmonella. This review, based on an understanding of the stages of Salmonella transmission and an egg's self-protection mechanisms, highlights a comprehensive strategy toward Salmonella control in a process from egg production and handling to human consumption.

Quantification of Horizontal Transmission of Salmonella enterica Serovar Enteritidis Bacteria in Pair-Housed Groups of Laying Hens

An important source of human salmonellosis is the consumption of table eggs contaminated with Salmonella enterica serovar Enteritidis. Optimization of the various surveillance programs currently implemented to reduce human exposure requires knowledge of the dynamics of S. Enteritidis infection within flocks. The aim of this study was to provide parameter estimates for a transmission model of S. Enteritidis in laying-type chicken flocks. An experiment was carried out with 60 pairs of laying hens. Per pair, one hen was inoculated with S. Enteritidis and the other was contact exposed. After inoculation, cloacal swab samples from all hens were collected over 18 days and tested for the presence of S. Enteritidis. On the basis of this test, it was determined if and when each contact-exposed hen became colonized. A transmission model including a latency period of 1 day and a slowly declining infectivity level was fitted. The mean initial transmission rate was estimated to be 0.47 (95% confidence interval [CI], 0.30 to 0.72) per day. The reproduction number R(0), the average number of hens infected by one colonized hen in a susceptible population, was estimated to be 2.8 (95% CI, 1.9 to 4.2). The generation time, the average time between colonization of a "primary" hen and colonization of contact-exposed hens, was estimated to be 7.0 days (95% CI, 5.0 to 11.6 days). Simulations using these parameters showed that a flock of 20,000 hens would reach a maximum colonization level of 92% within 80 days after colonization of the first hen. These results can be used, for example, to evaluate the effectiveness of control and surveillance programs and to optimize these programs in a cost-benefit analysis.

NH 4+ secretion in the avian colon. An actively regulated barrier to ammonium permeation of the colon mucosa

Experiments were designed to characterize an active, electrogenic transport of NH 4 + ions across the colonic epithelium of the domestic fowl ( Gallus gallus). Colonic segments were isolated and stripped of underlying muscle. The mucosal epithelia were mounted in Ussing chambers and voltage-clamped to measure the short-circuit currents ( I SC) associated with transport. Bilateral addition of NH 4 + caused a dose-dependent outward current (negative I SC), with a Km of 34 ± 8 mM and a maximal current response of 311 ± 47 µA cm − 2 (12 ± 2 µEq cm − 2 h − 1 ). A similar effect was seen with unilateral addition of NH 4 + to the serosal (s) side, but not with mucosal (m) addition. Pre-treatment with 10 − 4 M amiloride exposed a net outward (negative) I SC, and serosal NH 4 + addition further increased this outward current with a Km of 53 ± 24 mM. Decreasing the bath pH from 7.3 to 6.0 did not affect the I SC response to NH 4 +. Unidirectional NH 4 + flux measurements revealed a net secretory flux (8.8 ± 3.1 µmol cm − 2 h − 1 s–m, versus 2.6 ± 1.4 µmol cm − 2 h − 1 m–s). Furthermore, the secretory flux closely matched the resulting change in I SC with serosal NH 4 +, showing that the transepithelial flux of NH 4 + could account for the outward current response. Addition of 50 nM bafilomycin A to the mucosal solution completely eliminated serosal to mucosal NH 4 + transport, implicating an apical V-type H +-ATPase in this transport process. The I SC response to NH 4 + was partially inhibited by ouabain, a blocker of the Na +/K +-ATPase, but only minimally affected by bumetanide, an inhibitor of the serosal Na +–K +–2Cl − cotransporter. Active NH 4 + extrusion across the mucosal membrane, combined with low permeability to NH 3 in this tissue, allow for maintenance of steep ammonia gradients across the colonic epithelium and protection from ammonia toxicity. Furthermore, these studies indicate that the hen colon may be a useful new model system for the study of NH 4 + transport.

Evaluation of the bacterial diversity in cecal contents of laying hens fed various molting diets by using bacterial tag-encoded FLX amplicon pyrosequencing

Laying hens are typically induced to molt to begin a new egg-laying cycle by withdrawing feed for up to 12 to 14 d. Fasted hens are more susceptible to colonization and tissue invasion by Salmonella enterica serovar Enteritidis. Much of this increased incidence in fasted hens is thought to be due to changes in the native intestinal microflora. An alternative to feed withdrawal involves feeding alfalfa meal crumble to hens, which is indigestible by poultry but provides fermentable substrate to the intestinal microbial population and reduces Salmonella colonization of hens compared with feed withdrawal. The present study was designed to quantify differences in the cecal microbial population of hens (n = 12) fed a typical layer ration, undergoing feed withdrawal, or being fed alfalfa crumble by using a novel tag bacterial diversity amplification method. Bacteroides, Prevotella, and Clostridium were the most common genera isolated from all treatment groups. Only the ceca of hens undergoing feed withdrawal (n = 4) contained Salmonella. The number of genera present was greatest in the alfalfa crumble-fed group and least in the feed withdrawal group (78 vs. 54 genera, respectively). Overall, the microbial diversity was least and Lactobacillius populations were not found in the hens undergoing feed withdrawal, which could explain much of these hens’ sensitivity to colonization by Salmonella.

Campylobacter in Finnish Organic Laying Hens in Autumn 2003 and Spring 2004

A total of 642 fecal samples and 360 table eggs from Finnish organic laying hens were collected in autumn 2003 (19 farms) and spring 2004 (17 farms) and studied for the presence of Campylobacter. In autumn, 84% of the farms were positive for Campylobacter and in spring, 76%. The percentage of positive samples within a flock varied between 5 and 100%. In addition, Campylobacter was isolated in a single eggshell sample. Campylobacter jejuni was the species isolated most often, although Campylobacter coli was detected on 3 farms in autumn and on 4 farms in spring. KpnI pulsed-field gel electrophoresis genotyping revealed a high level of diversity among the isolates; 47 different patterns were detected among a total of 162 isolates studied. On most of the farms, the genotypes identified in autumn and spring were different, also indicating temporal diversity among colonizing isolates. However, some predominant persistent genotypes were also detected among the isolates. These results suggest that the pool of colonizing isolates may include both variants with capability for persistent intestinal colonization in hens as well as variants with short-term colonization characteristics. In antimicrobial susceptibility testing, the majority of isolates were susceptible to ciprofloxacin, tetracycline, ampicillin, and nalidixic acid. On 2 farms, isolates resistant to nalidixic acid and to ciprofloxacin were detected. In conclusion, Finnish organic laying hens are often colonized by a diversity of Campylobacter pulsed-field gel electrophoresis genotypes.

Comparison of Salmonella enterica Serovar Enteritidis Levels in Crops of Fed or Fasted Infected Hens

Long-term feed withdrawal has been shown to increase ileocecal intestinal colonization and fecal shedding of Salmonella enterica serovar Enteritidis in challenged hens. Less information is available regarding effects of fasting on crop colonization. Two trials were conducted to compare effects of 14-day feed withdrawal vs. full feed on crop colonization in hens challenged with Salmonella Enteritidis. The levels of Salmonella Enteritidis in the crops of fasted hens were significantly higher than in nonfasted hens on days 3 and 10 and days 3, 9, and 16 postinfection (PI) in trials 1 and 2, respectively. Fecal shedding of Salmonella Enteritidis was significantly increased in the fasted hens on day 10 PI in trial 1. Analysis of crop IgA anti-Salmonella Enteritidis lipopolysaccharide levels in crop lavage samples of hens in trial 1 revealed a humoral response PI in both treatment groups with no significant differences, although peak response for fasted hens occurred 1 wk later. Histologic evaluation of hematoxylin and eosin-stained crop sections from trial 1 birds revealed mild to moderate heterophilic infiltration within the crop lamina propria (LP) or LP and epithelium of nonfasted infected hens at 24 and 96 hr PI. In comparison, heterophils in crops of fasted hens infected at this time point were sparse, indicating a possible diminished heterophil response in the fasted birds. Multifocal areas of tissue inflammation, as indicated by marked heterophil infiltration, with necrosis and sloughing of epithelium, were observed in crops from fasted hens at day 11 PI (14th day of feed withdrawal) but not in the fed groups. This severe heterophilic inflammation was observed in both challenged and nonchallenged fasted hens, suggesting that some factor other than Salmonella Enteritidis was responsible. These results indicate that feed withdrawal can have a dramatic effect on the integrity of the crop and its ultimate response to infection.

Na/D-Glucose Cotransport and SGLT1 Expression in Hen Colon Correlates with Dietary Na +

We have tested whether separately varying the content of either Na or Cl in diets causes earlier observed increase in Na-coupled sugar and amino acid transport induced by high NaCl diets in hen colon. A comparison was also made between the dependence of the Na-coupled transport on a pure wheat/barley/soya diet against a diet with supplements of essential amino acids, fatty acids, vitamins, and trace elements, as a test for possible elimination of the cotransporters due to a deficient diet. Na/nutrient-coupled transport was measured as changes in short circuit current. The level of expressed Na/glucose cotransporters, SGLT1, due to dietary alterations was followed by quantitative Western blot and immunodetection of SGLT1 in colon, and the dietary effects on plasma aldosterone were assessed as well. An observed switch in transport from amiloride-sensitive electrodiffusive Na transport to phlorizin-sensitive Na/D-glucose cotransport and Na/amino acid–coupled transport is caused solely by increasing Na + in the diet. Thus, neither dietary Cl − nor the dietary supplements altered the expression of Na +-coupled nutrient transport processes. Corroborating these findings, only Na + in the diet increased the expression of SGLT1 in colon epithelium and suppressed aldosterone level in plasma.

Salmonella Colonization and Shedding Patterns of Hens Inoculated via Semen

Two experiments were conducted to determine the effect of inseminating hens with semen contaminated with marker strains of Salmonella enteritidis and S. typhimurium. Eggs were collected and examined for salmonellae. In Expt. 1, 3/57 (5.3%) of eggs from S. enteritidis-challenged hens and 2/50 (4.0%) of eggs from S. typhimurium-challenged hens were contaminated with salmonellae. Salmonellae were recovered from only the shell. In Expt. 2, however, no eggs from S. typhimurium-challenged hens were contaminated; 2/73 (2.7%) of the eggs from S. enteritidis-challenged hens were contaminated. In Expt. 1, S. typhimurium was present in 30% of the oviducts and 20% of the ovaries; S. enteritidis was present in 20% of the oviducts and 20% of the ovaries. No salmonellae-containing oviducts or ovaries were found in either S. enteritidis- or S. typhimurium-challenged hens in Expt. 2. S. enteritidis and S. typhimurium were found in fecal samples taken 24 hr after insemination, but only S. enteritidis was fecally shed 7 days after insemination (20% in Expt. 1). Data indicate that semen may severe as a vehicle for transmission of salmonellae to the hen, which may result in sporadic production of contaminated eggs.

Mucosal acidification and an acid microclimate in the hen colon in vitro.

Experiments were performed on isolated, stripped colonic epithelia of low-salt-adapted hens (Gallus domesticus) in order to characterize acid secretion by this tissue. With symmetric, weak buffer solutions, colonic epithelia acidified both mucosal and serosal sides. Titration measurements of the mucosal acidification rate (pH-stat technique) averaged 1.63 +/- 0.25 microEq.cm-2.h-1. Mucosal acidification was also evident in colons from high-salt-adapted birds and in low-salt-adapted coprodeum, but was completely abolished in the high-salt coprodeum. Mucosal acidification by low-salt-adapted colonic epithelium was unaffected by sodium replacement, mucosal amiloride (10(-3) mol.l-1), and serosal ouabain (5 x 10(-4) mol.l-1), although all three treatments significantly reduced or reversed the short-circuit current. Acetazolamide (10(-3) mol.l-1, serosal) reduced mucosal acidification by 15% and simultaneously increased short-circuit current by a similar amount. Colonic epithelia incubated in glucose-free solutions had significantly lower acidification rates (0.59 +/- 0.13 microEq.cm-2.h-1, P < 0.002 versus controls) and addition of glucose (15 mmol.l-1), but not galactose, partially restored acidification to control levels. Anoxia (N2 gassing) completely inhibited short-circuit current, but reduced acidification by only 30%. A surface microclimate pH, nearly 2 pH units more acidic than the bath pH of 7.1-7.4, was measured in low-salt-adapted colon and coprodeum. The acid microclimate of both tissues was partially attenuated by adaptation to a high-salt diet. Colonic microclimate pH was dependent on the presence of glucose and sensitive to the bath pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Protective Effect of Used Poultry Litter and Lactose in the Feed Ration on Salmonella enteritidis Colonization of Leghorn Chicks and Hens

The effect of dietary administration of lactose and used poultry litter, containing cecal and fecal droppings from adult broilers, was evaluated for protective effects against Salmonella enteritidis colonization in leghorn chicks and 16-week-old hens. The addition of used litter as 5% of the feed ration significantly decreased (P < 0.01) Salmonella cecal and organ colonization in the chicks. Provision of used litter or used litter and lactose in the feed failed to provide protection against Salmonella colonization in the hens. The results indicated that resistance to S. enteritidis colonization may be effectively increased in leghorn chicks by exposure to adult intestinal flora present in used litter. Furthermore, the results suggest that microbiological strategies employing adult intestinal microflora that increase Salmonella colonization resistance in young chicks may be ineffective in older hens.

Effects of propionate on the acid microclimate of hen ( Gallus domesticus) colonic mucosa

1. 1. Short-chain fatty acid absorption in hen colon is protonated across the apical border coupled to an apical electrogenic proton pump. 2. 2. The surface pH of the isolated colonic epithelium was 6.27 ± 0.05, when incubated in Krebs-phosphate buffer pH 7.0. 3. 3. Propionate 7 and 40mmol/l in the incubation medium (pH 7.0) increased microclimate pH to 6.47 ± 0.04 and 6.56 ± 0.04. Inhibition of metabolic activity by potassium cyanide 1 mmol/1 increased surface pH to 6.66 ± 0.06. 4. 4. The calculated concentration of propionic acid in the microclimate is near-linearly related to the propionate concentration. Thus, the acid microclimate is not responsible for the Michaelis-Menten like kinetics of propionate transport.

Involvement of non-classical 5-HT receptor in serotonin and cisapride induced secretion in hen colon

1. In hen colon 5-HT induces a tetrodotoxin-resistant, bumetanide-sensitive, chloride secretion, positively coupled with adenylate cyclase activity. 2. The 5-HT receptor mediating this response seems non-classical since it cannot be blocked by 5-HT 1.like, 5-HT 2 or 5-HT 3 antagonists. 3. Effects are presented of new putative 5-HT agonists and antagonists on short circuit current and cord conductance in the hen colon, using the Ussing chamber technique. 4. The substituted benzamides, cisapride and BRL 24924, induced a dose-dependent short circuit currents but both with less potency than 5-HT. 5. Cisapride mediated this dose-dependent bumetanide sensitive response mainly by release of acetylcholine, since atropine reduced cisapride response by 70%. 6. Neither BRL 24924, 5-HTP-DP, ketanserin, ICS 205–930, prazosin, yohimbine, atropine nor piroxicam, covering the 5-HT 1p, 5-HT 2p, 5-HT 2, 5-HT 3, 5-HT 4, adrenergic and muscarinic receptor types and the prostaglandin synthesis, altered 5-HT induced increases in short circuit current and cord conductance. 7. Results suggest (a) cisapride mediates it's response mainly by releasing acetylcholine, which then stimulates muscarinic receptors to release 5-HT. (b) Involvement of a non-classical 5-HT receptor subtype in 5-HT induced chloride secretion in hen colon.

Aldosterone modulates electrogenic Cl secretion in the colon of the hen (Gallus domesticus).

The regulation of Na and Cl transport in hen colon by mineralocorticoids was investigated with isolated epithelia in vitro by histological and electrophysiological techniques. The electrogenic transport of Na and Cl was measured in Ussing chambers by the short-circuit current technique and was identified by the specific inhibitors amiloride and bumetanide or by the secretagogue theophylline. Hens were maintained either on low (LS)- or on high-NaCl diets (HS), and the plasma aldosterone (PA) levels of these groups were measured with radioimmunoassay. A group of HS hens received injections of aldosterone at a 6-h schedule before experiments. A group of LS hens was resalinated, and experiments were carried out at a 24-h interval for up to 3 days after resalination. The LS diet stimulated PA levels ninefold, compared with HS hens. Na transport was modulated by the hormonal stimulus in a way that the apical Na entry switched from an electrogenic Na-amino acid-hexose cotransport system completely to an amiloride-sensitive Na channel. Electrogenic Cl secretion was induced by theophylline and was inhibited by bumetanide. NaCl deprivation, resalination or aldosterone injection modulated electrogenic Cl secretion in parallel between 7 (HS) and 14.4 mu eq.cm-2.h-1 (LS), with pronounced alteration in tissue conductance. These findings reveal a new action of aldosterone that, besides stimulating Na absorption, also directly or indirectly modulates Cl secretion.

Two types of chloride channels in hen colon epithelial cells identified by patch-clamp experiments

Freshly isolated epithelial cells from hen colon were investigated using the patch-clamp technique. The aim of this investigation was to characterise the cellular conducting site for Cl- secretion. In cell-attached mode two types of Cl(-)-channels were found. Both showed distinct outward rectification. The channel types differed in single channel conductances and the marked voltage dependence of the open probabilities. A low conductance Cl(-)-channel was observed with a mean conductance at negative holding potentials of g- = 9 pS, and of g+ = 34 pS at positive potentials. This channel was predominantly open at negative potentials, corresponding to cell hyperpolarization. The second channel type observed had conductances of g- = 35 pS and g+ = 77 pS, and showed increasing open probabilities with increasing holding potentials (cell depolarisation). Both channel types were blockable by the Cl(-)-channel blocker NPPB. These data in combination with previously published transepithelial transport data on hen colon indicate that these channels are the Cl- secretory sites in colon epithelium.

Intestinal transport of potassium. Effects of changing apical and basolateral influx of sodium in the isolated mucosa of the hen ( Callus domesticus) colon

1. 1. Net potassium secretion (J net K) by the sodium-depleted hen's colon (low sodium colon) is 0.17 ± 0.07 μmol/cm 2·hr Amiloride or ouabain eliminates short circuit currents (I sc) of 16–20 μmol/cm 2· hr without affecting J sm K. 2. 2. In the NaCl-loaded hen's colon (high sodium colon) stimulating I sc by (a) glucose, (b) amino acids, and inhibiting with (c) ouabain changes J net K from 0.08 ± 0.04 to (a) 0.42 ± 0.07, to (b) 0.60 ± 0.07 to (c) 0.13 ± 0.13 μmol/cm 2·hr. 3. 3. In both colonie types theophylline increases and bumetanide decreases J net K by 1 μmol/cm 2·hr. 4. 4. Conclusion: Apical membranes of sodium-absorbing and chloride-secreting cells of the high sodium colon are potassium permeable. In the low sodium colon sodium-absorbing cells have potassiumimpermeable apical membranes.

In vitro studies of theophylline-induced changes in Na, K and Cl transport in hen ( Gallus domesticus) colon suggesting bidirectional, basolateral NnK2Cl cotransport

1. 1. In isolated mucosa from a NaCl-loaded hen theophylline stimulates both unidirectional chloride fluxes (J Cl msand J Cl ms). Conductive and electroneutral exchange processes, besides a bumetanidesensitive, rheogenic process contribute. 2. 2. The bumetanide-sensitive fraction of the theophylline-induced ΔJ Cl ms is sodium-dependent. 3. 3. Incubation in nominally K +-free solutions reduces the bumetanide-sensitive fraction ΔJ Cl ms more than treatment with ouabain. 4. 4. With respect to chloride the bumetanide-sensitive fraction of ΔJ Cl ms has a Hill coefficient of 1.93 ± 0.03, a J max of 12.9 ± 0.2 μ mol/cm 2· hr and a K 1 2 of 73 ± 1 mmol/l . 5. 5. After ouabain treatment ΔJ ms Cl and ΔJ ms Cl are equally sensitive to bumetanide, while ΔJ ms Cl is bumetanide insensitive without ouabain treatment.