Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SEROSITIS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60Linked to original sources
PubMed1979

Drug uptake into everted intestinal sacs. I. Enhancement by hypertonicity.

The transfer of the cationic drugs, pralidoxime (PAM) and tetraethylammonium, and anionic ampicillin from the mucosal-to-serosal sides of everted rat jejunal sacs is enhanced by mucosal hypertonicity. PAM uptake, which is proportional to initial mucosal concentrations up to 2.3 mM, is enhanced by mucosal hypertonicity due to addition of sodium, potassium, lithium and choline chloride, sodium sulfate, and the nonionic solutes, urea, sucrose, and mannitol. Bicarbonate, Tris, or phosphate buffer and the presence of magnesium and calcium do not affect this hypertonicity-induced acceleration of PAM passage. Serosal osmolality has no effect on transfer and mucosal hypertonicity is equally effective in the presence and absence of a transmural osmotic gradient. This observation and minimal changes in the concentration of inulin placed in the sacs suggest that fluid shifts and solvent drag are not responsible for the enhanced mucosal-to-serosal transfer of PAM from hypertonic buffer. Mucosal hypertonicity at 450 mosmol/kg causes reversible enhancement of PAM transfer, whereas the effect of 600 mosmol/kg cannot be reversed by replacing the tissue in isotonic buffer. The effect of osmotic manipulation on PAM transfer across the intestine thus differs from its effect on the passage of other ionized species and drugs across other epithelia.

Ampicillin↗
PubMed1980

In vitro primate gastric mucosa: electrical characteristics.

Ion transport by the resting, isolated, rhesus gastric mucosa was assessed under conditions of minimal diffusion limitation to oxygen by 1) the substitution of Na+ and Cl- of the bathing solutions with less permeant ions, 2) the drugs amiloride and ouabain, and 3) estimation of net fluxes of 22Na by methods designed to circumvent the problem of poorly matched tissues. The mucosae developed potential differences of 51.3 +/ 3.5 mV, serosal side positive and had conductances of 5.56 +/- 0.30 mS x cm-2. The permeabilities of the tissues to D-mannitol were between 7.80 x 10(-7) and 3.15 x 10(-7) cm x s-1. The relatively high conductance of this epithelium in the absence of significant edge damage and a low (32%) paracellular conductance stems mainly from a passive permeability to Cl-; active absorption of Na+ and active secretion of Cl- contribute equally to the short-circuit current. The mucosal entry step for Na+ is amiloride sensitive, whereas the serosal exit step can be inhibited by ouabain. The entry step for Cl- at the serosal membrane is possibly sodium dependent.

Amiloride↗
PubMed1980

Effect of serotonin on active electrolyte transport in rabbit ileum, gallbladder, and colon.

The effect of serotonin on active electrolyte transport was evaluated in vitro in epithelial sheets of rabbit ileum, gallbladder, and colon under short-circuited conditions. Serotonin added to the serosal surface of rabbit ileum caused a dose-dependent short-lived increase in short-circuit current and a more prolonged equal effect on net Na and Cl fluxes. The latter consisted primarily of inhibition of mucosal-to-serosal fluxes of both Na and Cl. In addition serosal serotonin decreased ileal Na influx from the mucosal solution into the epithelium, suggesting an effect on Na absorption. Serotonin did not alter all aspects of ileal absorptive function and did not affect glucose-dependent Na absorption. Consistent with serotonin acting by inhibiting NaCl absorption in the ileum, serotonin induced equal inhibition of net Na and Cl absorption in rabbit gallbladder (which has a linked Na and Cl absorptive process) but had no effect on rabbit colon (which lacks a linked Na and Cl absorptive process). In addition, adenosine 3',5'-cyclic monophosphate and serotonin both appeared to alter the same ileal NaCl absorptive process, since following stimulation of ileal secretion with the maximum concentration of theophylline, addition of serotonin did not cause any further effects.

Animals↗
PubMed1981

Sugar absorption and secretion by winter flounder intestine.

Transport of sugars by winter flounder (Pseudopleuronectes americanus) intestine has been examined, and the following observations have been made. 1) No net absorption of D-galactose was found in controls; however, mucosally applied 0.1 mM phlorizin stimulated the mucosal-serosal flux with net sugar secretion. 2) Net absorption of methyl glycosides was inhibited by D-galactose, 0.1 mM ouabain, and phlorizin (without induction of secretion). 3) Net secretion of 2-deoxy-D-galactose was found without cellular accumulation of free sugar. The secretory process had a Km of 10 mM and was inhibited by serosally applied 0.1 mM phloretin, bilateral replacement of Ringer Na+ by choline, serosal ouabain, and D-galactose. 4) No net absorption or secretion of 2-deoxy-D-glucose was found with a variety of experimental conditions. 5) At least two active transport systems for sugars appear to be operative in the flounder intestine: a conventional Na+-dependent sugar transport system across the brush border that allows net absorption and a Na+-dependent secretory system that apparently also operates across the mucosal border. Because D-galactose is transported by both systems, there is no net flux of this sugar. Several possible models for the net secretory system are discussed.

Animals↗
PubMed1981

Transepithelial calcium transport by rat cecum: high-efficiency absorptive site.

Transepithelial calcium transport has been investigated in rat cecum under in vitro voltage-clamp conditions. Under short-circuit conditions, the cecum behaves as a relatively tight epithelium for calcium fluxes, where mucosal-to-serosal (JCam leads to s) flux exceeds the reverse flux by at least 15-fold. JCanet is abolished in the presence of 1 mM N-ethylmaleimide, is inhibited by 40% with 1 mM ouabain, and is decreased by at least 60% when medium sodium is replaced by choline. Voltage-clamping experiments suggest that both electroneutral- and electrogenic-mediated calcium fluxes traverse the cell in the mucosal-to-serosal direction. Serosal-to-mucosal flux is purely diffusional and probably constrained to the paracellular pathway. In rats weighing less than 175 g, a low-calcium diet has no significant stimulatory effect on JCam leads to s, but a high-calcium diet markedly reduces this flux. These results suggest that the cecum possesses the highest density of calcium transport sites in the rat intestine and is ideally suited for bulk calcium absorption, which may be "down regulated" in response to an increased calcium load in growing animals.

Animals↗
PubMed1982

Chloroquine stimulates absorption and inhibits secretion of ileal water and electrolytes.

The effects of chloroquine diphosphate, a drug with "'membrane-stabilizing" properties, were studied on basal ileal absorption and on ileal secretion induced by increased intracellular cAMP levels and calcium (serotonin). The studies were performed on rat (in vivo) and rabbit ileum (in vitro). Intraluminal chloroquine (10(-4) M) reversed cholera toxin- and theophylline-induced secretion in rat ileum but did not alter the cholera toxin- and theophylline-induced increases in cAMP content. Addition of chloroquine (10(-4) M) to the mucosal surface of rabbit ileum did not alter basal active electrolyte transport or the serotonin-induced decreased Na and Cl absorption but inhibited the theophylline-induced C1 secretion. Addition of chloroquine (10(-4)) M) to the serosal surface stimulated net Na and Cl absorption. This effect may involve intracellular calcium. Chloroquine increased the rabbit ileal calcium content and decreased 45Ca2+ influx from the serosal surface. Both the mucosal and serosal effects of chloroquine described led to a net increase in absorptive function of the intestine and should prove useful in developing treatment of diarrheal diseases.

Absorption↗
PubMed1983

Transmural fluxes of 5-hydroxytryptamine in guinea pig ileum.

Transmural movement of 5-hydroxytryptamine (5-HT) was studied in guinea pig small intestine in vitro in order to test the hypothesis that there is mucosal 5-HT barrier in this species. Segments of guinea pig ileum were mounted as flat sheets in flux chambers or were everted and perfused. Mucosal-to-serosal (Jm leads to s) and serosal-to-mucosal (Js leads to m) fluxes of 5-HT were measured in the absence of 5-HT gradients and under open- or short-circuited conditions. The results indicated that substantial transmural movement of 5-HT occurred in these preparations. Both Jm leads to s and Js leads to m were linear functions of the 5-HT concentration over a range of 1-30 microM and were not significantly different in the two directions. Addition of 2,4-dinitrophenol to both sides of the tissue reduced short-circuit current to zero and increased both tissue conductance and unidirectional 5-HT fluxes. These results suggested that the 5-HT fluxes across the guinea pig ileum occurred by passive mechanisms. Fluxes of 5-HT across preparations with the muscularis externa removed were not significantly different from fluxes across intact preparations. Mucosal-to-serosal 5-HT fluxes in everted perfused sacs were comparable with fluxes in the flat-sheet preparations. The data are not consistent with the hypothesis of a "tissue barrier" that functions to prevent 5-HT from reaching serotonergic receptors on enteric ganglion cells or enteroendocrine cells.

2,4-Dinitrophenol↗
PubMed1983

Effects of scorpion venom on electrolyte transport by rabbit ileum.

Scorpion venom, which depolarizes nerves, was used to obtain further evidence that intramural nerves affect ion transport by the rabbit ileum. Ileal epithelium, stripped of muscularis propria, was mounted in a flux chamber modified to permit electrical field stimulation (EFS) of the tissue. Response of the short-circuit current (Isc) to venom was most rapid on the serosal surface, and the response was eliminated by tetrodotoxin. Isc response was influenced by venom batch number and by factors within the tissue. Venom (10 micrograms/ml) and EFS each caused chloride secretion by reducing mucosal-to-serosal movement and by increasing serosal-to-mucosal movement. Sodium transport and residual ion fluxes did not change. In the presence of venom, EFS caused no further changes in ion transport, but tissues still responded to glucose and to aminophylline. The early peak of Isc was reduced about 40% by atropine, implying that acetylcholine, released by venom, stimulates muscarinic receptors. The blockade of the Isc response to venom with tetrodotoxin is further evidence that venom depolarizes intramural nerves and liberates transmitters that cause chloride secretion. The identity of the other transmitters is not known.

Animals↗
PubMed1983

Dantrolene and basal ileal sodium and chloride transport: involvement of calcium stores.

The effect of dantrolene on active ion transport in rabbit ileum was determined using the Ussing chamber short-circuiting technique. Dantrolene prevents the release of calcium from intracellular stores in skeletal muscle and was used to probe the role of intracellular calcium stores in intestinal ion transport. A saturated solution of dantrolene (approx 25 microM) decreased ileal short-circuit current and potential difference, increased conductance and mucosal-to-serosal and net Na and Cl fluxes, but did not alter serosal-to-mucosal Na and Cl fluxes. The dantrolene stimulation of active Na and Cl absorption was specific since it did not alter glucose-dependent Na absorption, transport changes caused by Ca2+ ionophore A23187, or the increase in short-circuit current caused by dibutyryl cAMP or theophylline. These effects were associated with an increase in total ileal calcium content and a decreased rate of 45Ca2+ efflux without any change in 45Ca2+ influx from the serosal or mucosal surfaces. These findings are consistent with an effect of dantrolene to stimulate active ileal Na and Cl absorption by a mechanism involving lowered cytosol Ca2+ levels and compatible with trapping calcium in intracellular stores. It thus appears as if intracellular calcium stores have an important role in the control of basal ion transport in the intestine.

Animals↗
PubMed1983

Role of tight-junctional pathways in bile salt-induced increases in colonic permeability.

The effects of a dihydroxy bile salt, taurochenodeoxycholate (TCDC), on the permeability and conductance of isolated, short-circuited segments of the rabbit descending colon were examined using conventional Ussing chamber techniques. Increasing concentrations of TCDC (1-4 mM) produced dose-dependent increases in sodium backflux (JNas leads to m) and tissue conductance (Gt) when applied to either the mucosal or serosal salines. However, mucosal addition was twice as potent in increasing JNas leads to m and Gt at 4 mM. Tracer experiments indicated that the transepithelial serosal-to-mucosal fluxes of sodium and mannitol are via an aqueous, unrestricted, free-solution pathway, while albumin movements are restricted through this pathway both in the absence and presence of mucosal TCDC. The changes in JNas leads to m, JMans leads to m, and Gt caused by 4 mM mucosal TCDC were largely reversed by rinsing the mucosal chamber with fresh buffer. It was also observed that osmotically induced volume flows in the serosal-to-mucosal direction could offset or reverse the changes in Gt produced by 2 mM mucosal TCDC, suggesting that the enhanced conductance pathway is in series with the lateral intercellular spaces. Taken together, these results suggest that low concentrations of TCDC alter the integrity of tight-junctional complexes between the epithelial cells of the rabbit colon.

Animals↗
PubMed1984

Further studies on sudden potential drop in gastric mucosa.

The sudden potential drop (SPD) with its associated resistance drop, previously noted during anoxia when serosal pH was slightly decreased, can also be produced by substrate deprivation and reversed by addition of substrate. During a critical portion of the response, alternate stable high and low potential difference states can be selected by current pulsing. High Ca2+ in the serosal solution prevents the SPD response, and any condition preventing an SPD response will reverse the post-SPD potential. Although pH 1 mucosal solutions do not damage the tissue, an SPD under these conditions results in permanent loss of secretory activity, apparently due to increased H+ permeability in the post-SPD state. Cl-, Rb+, and urea fluxes are unchanged by the SPD. Since gastric anoxia and mild serosal acidosis might be expected during strong sympathetic stimulation, it is notable that an SPD can be produced in vivo by anoxia or vasoconstrictive drugs under conditions apparently in agreement with the in vitro requirements. This might provide a model system for studies of stress ulcer production. An equivalent circuit model for the SPD is presented, which agrees satisfactorily with the observations.

Aerobiosis↗
PubMed1985

Colonic potassium and chloride secretion: role of cAMP and calcium.

Stripped rabbit colonic mucosa was studied in vitro in Ussing chambers to further investigate the role of Ca in regulating K and Cl secretion stimulated by the divalent cation ionophore A23187, prostaglandin E1 (PGE1), or 8-bromo-cAMP (8BrcAMP). To assess the effects of these secretagogues on the paracellular shunt permeability, we measured the Na concentration dependence of the serosal-to-mucosal Na flux in the absence or presence of these stimuli. Results from these studies reveal that changes in net K and Cl secretion produced by secretory stimuli cannot be accounted for by a change in shunt permeability. The possible involvement of Ca in the secretory response of the colon to these stimuli was investigated by measuring the changes in Cl and K transport elicited by A23187, PGE1, or 8BrcAMP in the absence or presence of trifluoperazine (10(-4) M) added to the serosal bathing solution. Trifluoperazine alone did not significantly alter basal Na or Cl fluxes or short-circuit current (Isc) but did decrease transepithelial conductance (Gt) and the serosal-to-mucosal K flux. Pretreatment of the tissues with trifluoperazine significantly reduced or abolished the changes in K fluxes elicited by A23187, 8BrcAMP, or PGE1 without altering the changes in Cl transport, Isc, and Gt. These results suggest that K secretion induced by these secretagogues involves an increase in intracellular Ca concentration and may be mediated by calmodulin.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1986

Effect of sugars and amino acids on amphibian intestinal Cl- transport and intracellular Na+, K+, and Cl- activity.

The effect of glucose, galactose, and valine on intestinal Cl- transport and intracellular Cl-, Na+, and K+ activity was investigated in isolated segments of Amphiuma small intestine. By use of double-barreled Cl- -specific microelectrodes, it was observed that galactose and valine reduced the luminal membrane potential (psi m) and eliminated the difference between the Cl- equilibrium potential (ECl) and psi m, i.e., the Cl- accumulation potential (ECl-psi m) approached zero. Simultaneously, Cl- absorption (JnetCl) was reduced in short-circuited tissues and Na+ absorption was enhanced. In contrast, after exposure to glucose, psi m and ECl-psi m declined only transiently and JnetCl was unaltered. In tissues pretreated with galactose to reduce Cl- transport, addition of glucose to the serosal medium restored Cl- accumulation across the luminal membrane and the Cl- absorptive current. Glucose, galactose, and valine each reduced intracellular K+ activity significantly. Galactose and valine each increased [corrected] intracellular Na activity (aiNa) markedly, whereas glucose increased aiNa only slightly. In conclusion, intestinal ion transport can be limited by the availability of metabolic substrate. The nonmetabolized solutes galactose and valine inhibited Cl- uptake and net Cl- absorption while stimulating net Na absorption, as though net Na+ absorption has priority over Cl- transport at the cellular level. Cl- transport is reduced at both mucosal and serosal membranes. At the luminal membrane electrogenic Cl- uptake is slowed or a backleak of Cl- is enhanced; at the serosal membrane Cl- exchange with Na+ (and HCO3-) driven by the Na+ gradient is reduced. The availability of metabolizable glucose to the cell prevents the reduction in net Cl- absorption.

Amino Acids↗
PubMed1986

Potassium selectivity of frog gastric luminal membrane.

Transmural potential difference (PD) and resistance (R) changes after luminal or serosal instillation of K+ were determined under various conditions in chambered preparations of frog gastric mucosae. Potassium selectivity of the luminal membrane is indicated by the rapid reversal of the inverted PD of mucosae bathed in NaCl-free, choline sulfate (Ch2SO4)-Ringer on the serosal side and unbuffered hypertonic Ch2SO4 solution on the luminal side on luminal K+ instillation. The delta PD responses are significantly attenuated, however, in histamine-stimulated mucosae bathed in hypotonic or in burimamide-inhibited mucosae bathed in hyper- and hypotonic luminal media, which suggests that the K+ selectivity of the luminal membrane resides largely in the tubular cell apical membrane. Imposing a serosal-to-luminal transmucosal K+ gradient in both histamine-stimulated and omeprazole-inhibited mucosae also reversed the normal orientation of PD but not in those inhibited with burimamide. In the latter, the PD inversion was attenuated but maintained its normal orientation. These data suggest that burimamide, but not omeprazole, acts by blocking luminal membrane K+ conductance. The inverted PD in mucosae bathed in Cl-free media may thus be due partially or fully to K+ diffusion driven by the cell-to-lumen K+ gradient via the luminal K+ conductance pathway. These findings have implications for the controversy surrounding the postulated electrogenicity of the gastric proton pump.

Animals↗
PubMed1986

Effects of medium pH on duodenal and ileal calcium active transport in the rat.

To study the effect of pH on Ca active transport in vitro pH was varied from 7.1 to 7.7, and bidirectional transmural Ca fluxes were measured under short-circuited conditions across duodenum or ileum from rats fed either normal chow (NCD, 1.2% Ca) or low Ca (LCD, 0.002% Ca). Duodenum and ileum from rats fed LCD actively absorbed calcium at medium pH 7.4. Reduction in mucosal and serosal medium bicarbonate from 25 to 10 mM (pH 7.4 to 7.1) decreased duodenal net Ca absorption (Jnet) from 121 +/- 32 to 39 +/- 9 nmol X cm-2 X h-1 (P less than 0.02) and ileal Jnet from 74 +/- 13 to 22 +/- 6 (P less than 0.01). The decline in duodenal and ileal Ca Jnet was due to a decrease in the mucosal-to-serosal flux (Jm----s). Raising medium pH from 7.4 to 7.7 by increasing bicarbonate from 25 to 50 mM did not alter Ca Jm----s, serosal-to-mucosal flux (Js----m), or Jnet X Ca fluxes across ileum from rats fed NCD demonstrated net secretion. LCD ileal Jm----s was unaltered when pH was reduced from 7.4 to 7.1 by increasing the PCO2 content of the buffer from 30 to 81 mmHg while maintaining bicarbonate at 24 mM. The results indicate that in vitro conditions that simulate metabolic acidosis (low bicarbonate and pH, normal PCO2) inhibit 1,25D-mediate calcium Jm----s, whereas conditions that simulate respiratory acidosis have no effect on Ca fluxes. The present studies suggest that decreases in calcium Jm----s is by a primary alteration in transport of other ions rather than direct effect on Ca transport.

Animals↗
PubMed1987

Epithelial responses evoked by stimulation of submucosal neurons in guinea pig distal colon.

The influence of submucosal neurons on ion transport in the guinea pig distal colon was examined in muscle-stripped sheets of submucosa-mucosa set up in Ussing flux chambers. Spontaneous variations in potential differences (PD) and short-circuit current occurred ranging from positive currents associated with luminal negative PDs to negative currents with luminal positive PDs. Basal current in both groups was reduced by mucosal amiloride. In tissues with positive or negative short-circuit currents, unidirectional mucosal-to-serosal sodium fluxes were greater than serosal-to-mucosal fluxes and small net absorptive fluxes were present. Little or no chloride secretory flux was present. Electrical stimulation of submucosal neurons evoked a tetrodotoxin-sensitive increase in short-circuit current in tissues with positive or negative short-circuit currents. This was due to an increase in net chloride flux and little change in net sodium flux or residual flux. The increase in net chloride flux was due almost entirely to an increase in serosal-to-mucosal chloride flux and was associated with an increase in total tissue conductance. The stimulus-evoked response was reduced by atropine. These results suggest that stimulation of submucosal neurons that innervate the distal colonic epithelium evokes a large chloride secretory response that is due in part to release of acetylcholine at neuro-enterocyte junctions.

Amiloride↗
PubMed1988

Acid-base effects on ileal sodium chloride absorption in vitro.

Previous work from this laboratory has shown that in the intact animal, ileal sodium chloride absorption is responsive to alterations in systemic acid-base balance. In vitro studies were undertaken to determine the nature of the active transport process affected. Paired, unstripped ileal tissues from Sprague-Dawley rats were mounted in modified Ussing chambers, and unidirectional 22Na and 36Cl fluxes were measured under short-circuited conditions (Isc). Acid-base effects were examined by changing either bathing solution partial pressure of CO2 (PCO2) or HCO3 concentration or by the addition of HCl or NaOH to a non-HCO3 N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffer. When pH was decreased from 7.6 to 7.1, net sodium absorption increased twofold regardless of the means by which pH was changed. This increase was primarily accounted for by an increase in mucosal-to-serosal flux. Net chloride absorption was affected in a similar way, but the increase in absorption was primarily accounted for by an increase in mucosal-to-serosal flux only in the HEPES buffer. These changes were accompanied by reductions in Isc and residual flux. When all groups were considered, mucosal-to-serosal Na (JNam----s) and net Na (JNanet) fluxes correlated strongly with bathing solution pH (r = 0.84 and 0.94, respectively, P less than 0.01). These data indicate that an active ileal sodium chloride absorptive process is specifically responsive to changes in bathing solution pH. In addition, pH may affect ileal electrogenic chloride, HCO3, and/or H secretion.

Absorption↗
PubMed1989

Emergence of Na+-glucose cotransport in an epithelial secretory cell line sensitive to cholera toxin.

Epithelial properties and effects of cholera toxin (CT) and glucose were investigated in human rectal tumor cell line HRT-18. Addition of 10(-3) M dibutyryl adenosine 3',5'-cyclic monophosphate (DbcAMP), 10(-8) M vasoactive intestinal peptide, 10(-5) M epinephrine, and 10(-5) M forskolin to the serosal side and of 3.5 micrograms/ml CT to the mucosal side and of 2 micrograms/ml A23187 to both the serosal and mucosal sides raised short-circuit current (Isc). This rise was reversed by serosal addition of 5 x 10(-5) M bumetanide or 10(-4) M ouabain. In filters treated with CT, Isc and net chloride flux (JClnet) increased after 60 min from 0.05 +/- 0.008 and -0.04 in the Ringer to 0.32 +/- 0.05 and -0.33 mueq.h-1.cm-2, respectively. Addition of 10(-2) M glucose further raised Isc by stimulating net sodium flux (JNanet) (0.70 +/- 0.08 and + 0.58 mueq.h-1.cm-2, respectively). This additional augmentation of Isc was reversed by 0.5 mM phlorizin and was mimicked by 3-O-methyl-D-glucose. When the filters were stimulated by cAMP for 15 min, Isc was also enhanced by addition of glucose. In untreated filters, Isc, JNanet, and JClnet did not differ significantly before and after addition of glucose. It is concluded that HRT-18 cells in basal state do not display absorptive properties but secretory properties stimulated by CT. However they exhibit Na+-glucose cotransport once stimulated by either CT or cAMP.

Adenocarcinoma↗