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Cl/HCO3 antiport affects H-lactate symport activity at the basolateral pole of jejunum enterocyte.

BACKGROUND/AIMS: Under normal conditions the jejunal tract of the rat intestine absorbs HCO3. A basolateral Cl/HCO3 exchange, evidenced by means of membrane vesicles, could be involved in this process. Aim of this study was to investigate the anion exchange activity in the whole jejunal tract, where various transport systems could interact. METHODS: In the jejunal tract of rat intestine everted and incubated in vitro, the experimental conditions set up minimized loss of CO2 from the serosal solution, where pH and pCO2 were determined together with fluid and electrolyte transintestinal transport. RESULTS: The serosal pCO2 increase and pH decrease, evident during the experiment, could be antagonized by enhancing the 4,4-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) concentrations in the serosal fluid. Moreover high DIDS concentration affected fluid, sodium, lactate, bicarbonate and, although in the opposite direction, chloride transport, whilst they were ineffective on K flux. CONCLUSION: These results give evidence that in the basolateral membrane the inhibition of Cl/HCO3 antiport causes a diminution of lactic acid movement. Therefore we can hypothesize that Cl/HCO3 antiport facilitates basolateral H-lactate symport in order to carry endogenous lactic acid towards the blood stream.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

Evaluation of splanchnic perfusion and oxygenation during positive end-expiratory pressure ventilation in relation to subcutaneous tissue gases and pH. An experimental study in pigs with oleic acid-induced lung injury.

Evaluation of splanchnic perfusion and oxygenation was performed by measurements of serosal tissue oxygen tension (PserO2) and intramucosal pH (pHi) in relation to subcutaneous oxygen tension (PscO2), subcutaneous carbon dioxide tension (PscCO2) and subcutaneous pH (pHsc) in pigs subjected to oleic acid-induced lung injury during ventilation with increasing levels of positive end-expiratory pressure (PEEP). Lung injury resulted in a general hypoxia and redistribution of perfusion away from the subcutaneous and splanchnic tissues, illustrated by a decrease in PaO2 from 93 to 37 mm Hg (p < 0.01), PscO2 from 45 to 17 mm Hg (p < 0.01), PserO2 from 80 to 30 mm Hg (p < 0.01) and pHi from 6.84 to 6.74 (p < 0.05) and a decrease of porta flow from 0.77 to 0.57 l/min. Application of PEEP up to 10-15 cm H2O resulted in an increase of portal vein oxygen tension (PportaO2) from 21 to 34 mm Hg (p < 0.01), PscO2 from 17 to 26 mm Hg (p < 0.05) and PserO2 from 30 to 55 mm Hg (p < 0.05). At PEEP 20 cm H2O PserO2 decreased to 47 mm Hg (p < 0.05). Porta flow decreased continuously with increasing levels of PEEP. PserO2 correlated with PportaO2 (r = 0.7, p < 0.001). pHi correlated poorly with PportaO2 (r = 0.2) and porta flow (r = 0.4). PscO2 and PserO2 correlated well (r = 0.8, p < 0.001). In summary, splanchnic perfusion and oxygenation was better reflected by serosal oxygen tension than pHi in the colon. Changes in serosal oxygenation of the colon paralleled changes in subcutaneous tissue oxygenation.

Animals↗

Effect of capsaicin on bile secretion in the rat.

Capsaicin is a popular food ingredient. This study aimed to determine if capsaicin can affect bile flow and bile protein secretion, and the extent to which capsaicin can reach bile in the rat. The effect of capsaicin was studied in anesthetized rats equipped with cannulas inserted into the common bile duct. Capsaicin was administered by intragastric, intraduodenal (4-400 microg/ml; 10-1,000 microg/kg), intravenous (10 microg/kg) routes or applied on the serosal surface of the duodenum at 4 microg/ml. The administration of capsaicin decreased bile flow in comparison to the corresponding basal values, the maximum effect being reached at a concentration of 400 microg/ml of intragastric capsaicin (30.2%; p < 0.01), and 40 microg/ml (30.8%; p < 0.01) of intraduodenal capsaicin, 75 min after drug administration. Meanwhile, a decrease of 24.7 and 40% was observed 60 min after serosal and intravenous capsaicin administration, respectively. Biliary protein secretion was also reduced following capsaicin administration. High-performance liquid chromatography (HPLC) analysis showed that capsaicin was readily excreted into bile, peak levels were reached 75 or 60 min following its intragastric or intraduodenal administration, respectively (range 100-248 and 144-698.6 ng/ml after intragastric or intraduodenal capsaicin at 4-400 microg/ml, respectively). Capsaicin concentrations of 86 and 75 ng/ml could be detected in bile 15 min after intravenous administration or serosal application of the agent, respectively. Results suggest that capsaicin is readily absorbed after its intragastric or intraduodenal administration and goes through hepatobiliary excretion. Results also indicate that administration of capsaicin reduces bile flow and biliary proteins in the rat.

Animals↗

A new laser Doppler interface for the continuous measurement of the rat gastric mucosal blood flow.

The laser Doppler system (LD) has been proposed for a tissue blood flowmetry. However, its accuracy is dependent on the pressure and direction of the laser probe. Therefore, we have devised a new interface for the measurement of the gastric mucosal blood flow in rats keeping the probe constant in pressure and direction. This interface is a small cylinder with one end fixed upon the gastric serosa and the other end fixed externally upon the skin. The laser probe adjusts exactly in direction and pressure inside this button. The LD apparatus processes two shifted beams with a differential amplification and a root mean square. It delivers an index (LDI) from 0 to 10. This interface was tested in 3 groups of rats, comparing the mucosal (open stomach) with the serosal gastric LDI and the same serosal LDI with a 133Xe washout flow. Finally, the interface was used in control and restrained rats. The gastric serosal LDI was found to be similar to the mucosal LDI. The correlation between the LDI and the 133Xe washout flow was good, with a coefficient of 0.9. Finally, the LDI of the gastric mucosal blood was significantly different in control and stressed rats. This new interface makes the LD more reliable for the monitoring of gastric mucosal flowmetry. It has the same accuracy as the xenon washout and additionally it is simpler, cheaper and may be repeated or even be used continuously.

Animals↗

The influence of verapamil on calcium transport and uptake in segments of rat intestine.

The effects of verapamil on calcium transport and uptake in duodenal and jejunal segments of intestine in young male rats were determined using the everted gut-sac technique. Verapamil added to both the mucosal and serosal surface of duodenal segments decreased calcium transport and tissue uptake in a dose-related fashion over a concentration range of 1-2 mM. In jejunal segments verapamil (1 mM) added to both the mucosal and serosal surface reduced calcium transport but did not alter tissue uptake. Similarly, verapamil (1 mM) added to either the mucosal or serosal surface alone in duodenal segments reduced transport but did not depress tissue uptake. The results of this study indicate that verapamil alters calcium translocation in intestinal tissue in a fashion which is similar to that reported in other biological tissue.

Animals↗

Effects of antidiuretic hormone on the electrical properties of canine tracheal epithelium.

The canine tracheal epithelium causes net transport of Cl- from serosa to mucosa and of Na+ from mucosa to serosa. These processes are manifested by the short-circuit current which represents the algebraic sum of both fluxes. Antidiuretic hormone (ADH) alters the permeability of several epithelia. This work examines the effect and possible mechanism of action of ADH on the potential difference (PD), short-circuit current (ISC) and conductance (G) of canine tracheal epithelium. The epithelium was mounted in Ussing-type chambers containing Krebs-Henseleit solution at 37 degrees C (pH 7.4) and bubbled with 95% O2 and 5% CO2. PD was recorded on an Cole-Parmer recorder by means of the classical technique and ISC was recorded automatically using a voltage clamp. ADH (mucosal surface) significantly decreased PD, ISC and G in a dose-dependent fashion. Similar doses of ADH applied to the serosal side did not produce a significant effect. Angiotensin II (Agt II, serosal side) and amphotericin B (mucosal side) reversed the depressor effect of mucosal ADH. The effect of ADH was less when the Cl- serosa to mucosa movement was blocked by pretreatment with serosal furosemide. It is considered that ADH blocks apical membrane Cl-channels and that angiotensin reverses this effect by increasing apical membrane permeability to Cl-. Amphotericin B reverses the effect of ADH possibly by increasing Na+ absorption.

Amphotericin B↗

Rhein stimulates active chloride secretion in the short-circuited rat colonic mucosa.

In a short-circuited mucosa-submucosa preparation of the rat descending colon with preserved Meissner's plexus mounted as an everted sac rhein transiently increased the potential difference and short-circuit current (Isc) when administered serosally and mucosally, but serosal application was more effective. Maximal effects were obtained at rhein concentrations of 1.6 X 10(-4) and 3 X 10(-4) mol/l. Net chloride absorption was decreased. Indomethacin (5 X 10(-6) mol/l) did not inhibit the increase of Isc, but omission of calcium from the serosal side as well as tetrodoxin (2 X 10(-7) mol/l) decreased it by 50 and 60%. Mechanical removal of Meissner's plexus partly blocked the effect of rhein, too. It is concluded that rhein stimulates colonic secretion by a direct action on the epithelial cells together with an indirect action via neurohumoral mechanisms.

Animals↗

Influence of lanthanum on calcium transport and retention in the rat duodenum.

The present study examined the effects of lanthanum on calcium retention and transport in rat duodenal segments in vitro. Increasing the concentration of lanthanum from 0.1 to 10 mM in both the serosal and mucosal media produced a progressive decrease in tissue calcium retention and calcium transport. The addition of 10 mM lanthanum to the mucosal media alone reduced both calcium retention and transport. The addition of 10 mM lanthanum to the serosal media alone decreased calcium transport but did not alter total calcium retention by the duodenal segments. The results of this study indicate that lanthanum at a concentration of 1--10 mM acts at calcium transport sites in rat duodenum to reduce both calcium uptake and extrusion, with the net result that the addition of lanthanum to either the mucosal media, serosal media or both significantly reduced calcium transport.

Animals↗

Subepithelial hydrostatic pressure may regulate plasma exudation across the mucosa.

This study demonstrated in guinea pig tracheal tubes in vitro that small increases in serosal hydrostatic pressure caused significant mucosal crossing of serosal macromolecules. Reversibility and repeatability of this passage agree with inflammatory stimulus-induced appearance of exuded plasma in airway lumen in vivo. Bradykinin, histamine, and terbutaline, which induce and inhibit, respectively, plasma exudation in vivo, were without effect on the present in vitro permeability. Carbachol, similar to histamine, contracted the trachea, and did not increase, but rather decreased the pressure-induced luminal entry of serosal macromolecules. It is proposed that a plasma-exudation-induced hydrostatic pressure load transiently separates epithelial cells, providing a direction-selective and non-injurious intercellular pathway for passage of bulk plasma exudate into the airway lumen. This mechanism would allow potent plasma protein systems to operate on mucosal surfaces at sites of insults without compromising the mucosa as a barrier to luminal solutes.

Animals↗

Development of intestinal carnitine transport in rats.

The intestinal transport of carnitine in suckling rats (12 and 16 days old) and weaned rats (28 and 75 days old) was studied in vitro using everted small intestinal sacs. The sacs were incubated in a mucosal medium without carnitine or with added carnitine at a 200-microM concentration. The release of endogenous carnitine and its esters into the serosal medium was greatest in the 12-day-old pups and lowest in the postweaning period. In contrast, the transport of carnitine from the mucosal to the serosal compartment was lowest in the 12-day-old pups and higher in the older groups. The present study suggests that the transfer of carnitine from the mucosal to the serosal compartment is influenced by the presence of endogenous carnitine in the intestinal mucosa, which in turn is determined by the age of the animals.

Aging↗

The effects of the natriuretic factor from uremic urine on sodium transport, water and electrolyte content, and pyruvate oxidation by the isolated toad bladder.

The urine of patients with chronic uremia contains a gel filtration fraction that is natriuretic in the rat. The effects of this fraction on the isolated urinary bladder of the toad were examined in the present studies. When added to the serosal surface of the bladder, a significant and substantial fall in short-circuit current and potential difference was observed. The changes began after a lag period of at least 10 min and continued over a period of 60 min. The decrease in short-circuit current at the end of 1 h averaged 44%. The same fraction from the urine of normal subjects produced no significant change in either short-circuit current or potential difference. When the isolated epithelial cells from the toad bladder were incubated in the presence of the inhibitor, intracellular sodium content increased significantly. There was no change in intracellular water content; hence the intracellular concentration of sodium increased by a mean of 7 meq/liter. The changes in intracellular potassium content and concentration were not satistically significant. When the isolated epithelia were incubated with the uremic factor, there was also a significant decrease in pyruvate utilization in relation to cells from paired hemibladders incubated in the absence of the fraction. The fraction from normal subjects produced no change in either intracellular sodium content or pyruvate oxidation. The results suggest that the inhibitor acts from the serosal surface, inhibits sodium transport across the serosal barrier, and produces a decrease in substrate utilization in association with the change in transepithelial sodium transport.

Ammonium Chloride↗

Dopamine stimulation of active Na and Cl absorption in rabbit ileum: interaction with alpha 2-adrenergic and specific dopamine receptors.

The effects of dopamine on active intestinal ion transport have been evaluated. An epithelial sheet preparation of rabbit ileum was used in vitro with the Ussing chamber-voltage clamp technique. Dopamine, in the presence of 1 mM ascorbic acid, added to the serosal bathing solution caused a dose-dependent decrease in short-circuit current, with a half-maximal effect at 1.2 muM and maximal effect of -50 muA/cm(2) at 50 muM; dopamine decreased the potential difference, and increased the conductance and net Na and net Cl absorption. There was no effect on the residual ion flux. Dopamine did not alter the change in short-circuit current caused by mucosal glucose (10 mM) or serosal theophylline (10 mM). Mucosal dopamine had no effect. The effect of dopamine on short-circuit current was inhibited by the dopamine antagonists haloperidol and domperidone and the alpha(2)-adrenergic antagonist yohimbine; there was no effect of the alpha(1)-antagonist prazosin and the beta-antagonist propranolol. In addition, the alpha(2)-adrenergic agonist clonidine, but not the alpha(1)-agonist methoxamine caused a dose-dependent decrease in short-circuit current. The ileal effects of dopamine did not occur via conversion into norepinephrine or release of norepinephrine from the peripheral nerves since "peripheral sympathectomy" with 6-hydroxydopamine did not alter the dopamine-induced change in ileal short-circuit current. The dopamine effects were not associated with a change in basal ileal cyclic AMP content but were associated with a decrease in total ileal calcium content as measured by atomic absorption spectrometry and as estimated by (45)Ca(++) uptake. The decrease in calcium content could be attributed to a dopamine-induced decrease in (45)Ca(++) influx from the serosal surface. Because of the presence of dopamine in ileal mucosa and these effects on ileal electrolyte transport, it is possible that dopamine may be involved in the physiologic regulation of active intestinal electrolyte absorption.

Animals↗

Metalloproteinases and tissue inhibitor of metalloproteinases in mesothelial cells. Cellular differentiation influences expression.

Mesothelial cells play a critical role in the remodeling process that follows serosal injury. Although mesothelial cells are known to synthesize a variety of extracellular matrix components including types I, III, and IV collagens, their potential to participate in matrix degradation has not been explored. We now report that human pleural and peritoneal mesothelial cells express interstitial collagenase, 72- and 92-kD gelatinases (type IV collagenases), and the counterregulatory tissue inhibitor of metalloproteinases (TIMP). Our initial characterization of the mesothelial cell metalloenzymes and TIMP has revealed: (a) they are likely identical to corresponding molecules secreted by other human cells; (b) they are secreted rather than stored in an intracellular pool; (c) a primary site of regulation occurs at a pretranslational level; (d) phorbol myristate acetate, via activation of protein kinase C, upregulates expression of collagenase, 92-kD gelatinase, and TIMP, but has no effect on expression of 72-kD gelatinase; and (e) lipopolysaccharide fails to upregulate the biosynthesis of either metalloproteinases or TIMP. Of particular interest is the observation that the state of cellular differentiation has a striking influence on the expression of metalloenzymes and TIMP, such that epitheloid cells display a more matrix-degradative phenotype (increased 92-kD gelatinase and decreased TIMP) than their fibroblastoid counterparts. We speculate that mesothelial cells directly participate in the extracellular matrix turnover that follows serosal injury via elaboration of metalloproteinases and TIMP. Additionally, the reactive cuboidal mesothelium which is characteristic of the early response to serosal injury may manifest a matrix-degenerative phenotype favoring normal repair rather than fibrosis.

Adult↗

Effects of relaxin on mast cells. In vitro and in vivo studies in rats and guinea pigs.

The results of the current study demonstrate that relaxin inhibits histamine release by mast cells. This effect is related to the peptide concentrations, and could be observed in both isolated rat serosal mast cells stimulated with compound 48/80 or calcium ionophore A 23187, and in serosal mast cells isolated from sensitized guinea pigs and challenged with the antigen. The morphological findings agree with the functional data, revealing that relaxin attenuates calcium ionophore-induced granule exocytosis by isolated rat serosal mast cells. Similar effects of relaxin have also been recognized in vivo by light microscopic and densitometric analysis of the mesenteric mast cells of rats which received the hormone intraperitoneally 20 min before local treatment of the mesentery with calcium ionophore. Moreover, evidence is provided that relaxin stimulates endogenous production of nitric oxide and attenuates the rise of intracellular Ca2+ concentration induced by calcium ionophore. The experiments with drugs capable of influencing nitric oxide production also provide indirect evidence that the inhibiting effect of relaxin on mast cell histamine release is related to an increased generation of nitric oxide. It is suggested that relaxin may have a physiological role in modulating mast cell function through the L-arginine-nitric oxide pathway.

Animals↗

Compartmentalization of extracellular cGMP determines absorptive or secretory responses in the rat jejunum.

We examined potential mechanisms by which angiotensin subtype-2 (AT2) receptor stimulation induces net fluid absorption and serosal guanosine cyclic 3',5'-monophosphate (cGMP) formation in the rat jejunum. L-arginine (L-ARG) given intravenously or interstitially enhanced net fluid absorption and cGMP formation, which were completely blocked by the nitric oxide (NO) synthase inhibitor, N-nitro-L-arginine methylester (L-NAME), but not by the specific AT2 receptor antagonist, PD-123319 (PD). Dietary sodium restriction also increased jejunal interstitial fluid cGMP and fluid absorption. Both could be blocked by PD or L-NAME, suggesting that the effects of sodium restriction occur via ANG II at the AT2 receptor. L-ARG-stimulated fluid absorption was blocked by the soluble guanylyl cyclase inhibitor 1-H-[1,2,4]oxadiazolo[4, 2-alpha]quinoxalin-1-one (ODQ). Cyclic GMP-specific phosphodiesterase in the interstitial space decreased extracellular cGMP content and prevented the absorptive effects of L-ARG. Angiotensin II (ANG II) caused an increase in net Na+ and Cl- ion absorption and 22Na+ unidirectional efflux (absorption) from the jejunal loop. In contrast, intraluminal heat-stable enterotoxin of Escherichia coli (STa) increased loop cGMP and fluid secretion that were not blocked by either L-NAME or ODQ. These findings suggest that ANG II acts at the serosal side via AT2 receptors to stimulate cGMP production via soluble guanylyl cyclase activation and absorption through the generation of NO, but that mucosal STa activation of particulate guanylyl cyclase causes secretion independently of NO, thus demonstrating the opposite effects of cGMP in the mucosal and serosal compartments of the jejunum.

Angiotensin II↗

Sodium-iodide symporter mediates iodide secretion in rat gastric mucosa in vitro.

In vivo studies on rats have demonstrated that considerable amounts of iodide are transported from the bloodstream into the gastric lumen. The mechanisms for and functional significance of this transport are poorly understood. Active (driven by Na(+)/K(+)-ATPase) iodide transport into thyroid follicular cells is mediated by the sodium-iodide symporter (NIS), which is also abundantly expressed in gastric mucosa. We aimed to further investigate the iodide transport in gastric mucosa and the possible role of NIS in this transport process. Iodide transport in rat gastric mucosa was studied in vitro in an Ussing chamber system using (125)I as a marker. The system allows measurements in both directions over a mucosal specimen. A considerable transport of iodide (from the serosal to the mucosal side) was established across the gastric mucosa, whereas in the opposite direction (mucosa to serosa), iodide transport was negligible. Sodium perchlorate (NaClO(4)), a competitive inhibitor of NIS, and ouabain, an inhibitor of the Na(+)/K(+)-ATPase, both attenuated gastric iodide transport from the serosal to the mucosal side. To investigate a possible neuroendocrine regulation of the iodide transport identified to occur from the serosal to the mucosal side of the stomach, thyroid-stimulating hormone (TSH), thyrotropin-releasing hormone (TRH), vasoactive intestinal peptide (VIP), histamine, or nitric oxide donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP) was added. None of these substances influenced the iodide transport. We conclude that iodide is actively transported into the gastric lumen and that this transport is at least partly mediated by NIS. Additional investigations are needed to understand the regulation and significance of this transport.

Animals↗

Gender and age differences in systemic lupus erythematosus. A study of 489 Greek patients with a review of the literature.

We investigated whether gender and age influence the clinical course and outcome in systemic lupus erythematosus (SLE) patients. Thus, we analyzed the clinical and laboratory data of 489 SLE patients at presentation and during follow-up. In addition, disease activity score (using the European Consensus Lupus Activity Measure, ECLAM) and organ damage index (using the Systemic Lupus International Collaboration Clinics/American College of Rheumatology Damage Index, DI) were measured. Furthermore, data from both sexes were analyzed according to the following age groups: < 55 years(younger group) and > 55 years (older group). There were 68 men and 421 women, giving a ratio of 1:7. We found no differences in the mean age, mean age at diagnosis, disease duration as well as duration of follow-up between men and women. Young men presented more frequently with serositis and discoid lesions, while women presented with Raynaud's phenomenon (RP) and malar rash. Regarding the laboratory findings, young women presented more often with anti-Ro(SSA) and anti-La(SSB) antibodies, while increased levels of erythrocyte sedimentation rate (ESR) were found in old women. During follow-up, men had serositis and renal disease more frequently, while the women's group were found to complain of RP, photosensitivity and mucosal ulcers more frequently, especially in young women.Anemia, leukopenia, thrombocytopenia and elevated levels of ESR were also found more frequently in young women during follow-up. However, there were no significant differences concerning ECLAM and DI scores between the two gender groups. Using multiple logistic regression analysis, a statistically significant association of malar rash, discoid lesions, serositis, RP, anti-Ro(SSA)/ La(SSB) and increased ESR with sex was found independently of age, while only malar rash showed a statistically significant association with age independently of sex. Thus, we conclude that gender influences the clinical expresion of the disease independently of age, while both gender and age do not affect the overall damage score.

Adolescent↗

Relationship between adherence to study and clinic visits in systemic lupus erythematosus patients: data from the LUMINA cohort.

The aim of this study was to examine the relationship between nonadherence with study visits and with regularly scheduled clinic visits after adjusting for other patient and disease characteristics. One hundred and forty-one LUMINA patients with appointment data in the institutions' computerized systems (UAB and UTH) were studied. 'No shows' were assessed as the percentage of appointments not attended for either rheumatology, other clinics and LUMINA visits (from zero to 100%). Eighty-nine percent of the patients were women, 40% were Caucasians, 55% African-Americans and 5% Hispanics. 'No shows' to rheumatology were associated with non-Caucasian ethnicity, younger age, single marital status, lack of home ownership, 'no shows' to other clinics and to the LUMINA study, greater disease activity and to some disease manifestations (serositis, renal involvement, positive anti-dsDNA antibodies). In multivariable analyses, features predictive of rheumatology 'no shows' were lack of home ownership, 'no shows' to LUMINA study visits, renal involvement and serosal manifestations. Nonadherence with study visits and with regularly scheduled care at rheumatology clinics were associated. Other factors predictive of nonadherence to recommended care were lack of home ownership (a measurement of low socioeconomic status) and the presence of disease manifestations (i.e., renal or serosal involvement). These data should be considered when caring for patients with SLE.

Adult↗