Sodium and Calcium Inward Currents in Freshly Dissociated Smooth Myocytes of Rat Uterus

Freshly dissociated myocytes from nonpregnant, pregnant, and postpartum rat uteri have been studied with the tight-seal patch-clamp method. The inward current contains both I_Na and I_Ca that are vastly different from those in tissue-cultured material. I_Na is abolished by Na⁺-free medium and by 1 μM tetrodotoxin. It first appears at ∼−40 mV, reaches maximum at 0 mV, and reverses at 84 mV. It activates with a voltage-dependent τ of 0.2 ms at 20 mV, and inactivates as a single exponential with a τ of 0.4 ms. Na⁺ conductance is half activated at −21.5 mV, and half inactivated at −59 mV. I_Na reactivates with a τ of 20 ms. I_Ca is abolished by Ca²⁺-free medium, Co²⁺ (5 mM), or nisoldipine (2 μM), and enhanced in 30 mM Ca²⁺, Ba²⁺, or BAY-K 8644. It first appears at ∼−30 mV and reaches maximum at +10 mV. It activates with a voltage-dependent τ of 1.5 ms at 20 mV, and inactivates in two exponential phases, with τ''s of 33 and 133 ms. Ca²⁺ conductance is half activated at −7.4 mV, and half inactivated at −34 mV. I_Ca reactivates with τ''s of 27 and 374 ms. I_Na and I_Ca are seen in myocytes from nonpregnant estrus uteri and throughout pregnancy, exhibiting complex changes. The ratio of densities of peak I_Na/I_Ca changes from 0.5 in the nonpregnant state to 1.6 at term. The enhanced role of I_Na, with faster kinetics, allows more frequent repetitive spike discharges to facilitate simultaneous excitation of the parturient uterus. In postpartum, both currents decrease markedly, with I_Na vanishing from most myocytes. Estrogen-enhanced genomic influences may account for the emergence of I_Na, and increased densities of I_Na and I_Ca as pregnancy progresses. Other influences may regulate varied channel expression at different stages of pregnancy.     

Ultraviolet Photoalteration of Late Na+ Current in Guinea-pig Ventricular Myocytes

UV irradiation has multiple effects on mammalian cells, including modification of ion channel function. The present study was undertaken to investigate the response of membrane currents in guinea-pig ventricular myocytes to the type A (355, 380 nm) irradiation commonly used in Ca²⁺ imaging studies. Myocytes configured for whole-cell voltage clamp were generally held at −80 mV, dialyzed with K⁺-, Na⁺-free pipette solution, and bathed with K⁺-free Tyrode’s solution at 22°C. During experiments that lasted for ≈ 35 min, UVA irradiation caused a progressive increase in slowly-inactivating inward current elicited by 200-ms depolarizations from −80 to −40 mV, but had little effect on background current or on L-type Ca²⁺ current. Trials with depolarized holding potential, Ca²⁺ channel blockers, and tetrodotoxin (TTX) established that the current induced by irradiation was late (slowly-inactivating) Na⁺ current (I_Na). The amplitude of the late inward current sensitive to 100 μM TTX was increased by 3.5-fold after 20–30 min of irradiation. UVA modulation of late I_Na may (i) interfere with imaging studies, and (ii) provide a paradigm for investigation of intracellular factors likely to influence slow inactivation of cardiac I_Na.     

Sodium ATPase and Sodium/proton Antiporter Are Not Obligatory for Sodium Homeostasis of Enterococcus hirae at Acid pH

Enterococcus hirae grows in a broad pH range from 5 to 11. An E. hirae mutant 7683 lacking the activities of two sodium pumps, Na⁺-ATPase and Na⁺/H⁺ antiporter, does not grow in high Na⁺ medium at pH above 7.5. We found that 7683 grew normally in high Na⁺ medium at pH 5.5. Although an energy-dependent sodium extrusion at pH 5.5 was missing, the intracellular levels of Na⁺ and K⁺ were normal in this mutant. The Na⁺ influx rates of 7683 and two other strains at pH 5.5 were much slower than those at pH 7.5. These results suggest that Na⁺ elimination of this bacterium at acid pH is achieved by a decrease in Na⁺ entry and a normal K⁺ uptake.     

Nitration as a Mechanism of Na+, K+-ATPase Modification During Hypoxia in the Cerebral Cortex of the Guinea Pig Fetus

Previous studies have shown that hypoxia induces nitric oxide synthase-mediated generation of nitric oxide free radicals leading to peroxynitrite production. The present study tests the hypothesis that hypoxia results in NO-mediated modification of Na⁺, K⁺-ATPase in the fetal brain. Studies were conducted in guinea pig fetuses of 58-days gestation. The mothers were exposed to FiO₂ of 0.07% for 1 hour. Brain tissue hypoxia in the fetus was confirmed biochemically by decreased ATP and phosphocreatine levels. P₂ membrane fractions were prepared from normoxic and hypoxic fetuses and divided into untreated and treated groups. The membranes were treated with 0.5 mM peroxynitrite at pH 7.6. The Na⁺, K⁺-ATPase activity was determined at 37°C for five minutes in a medium containing 100 mM NaCl, 20 mM KCl, 6.0 mM MgCl₂, 50 mM Tris HCl buffer pH 7.4, 3.0 mM ATP with or without 10 mM ouabain. Ouabain sensitive activity was referred to as Na⁺, K⁺-ATPase activity. Following peroxynitrite exposure, the activity of Na⁺, K⁺-ATPase in guinea pig brain was reduced by 36% in normoxic membranes and further 29% in hypoxic membranes. Enzyme kinetics was determined at varying concentrations of ATP (0.5 mM-2.0 mM). The results indicate that peroxynitrite treatment alters the affinity of the active site of Na⁺, K⁺-ATPase for ATP and decreases the Vmax by 35% in hypoxic membranes. When compared to untreated normoxic membranes Vmax decreases by 35.6% in treated normoxic membranes and further to 52% in treated hypoxic membranes. The data show that peroxynitrite treatment induces modification of Na⁺, K⁺-ATPase. The results demonstrate that peroxynitrite decreased activity of Na⁺, K⁺-ATPase enzyme by altering the active sites as well as the microenvironment of the enzyme. We propose that nitric oxide synthase-mediated formation of peroxynitrite during hypoxia is a potential mechanism of hypoxia-induced decrease in Na⁺, K⁺-ATPase activity.     

Differences in open state of NBA-modified cardiac Na+ channels

Patch clamp recordings from neonatal cardiac Na⁺ channels treated with N-bromoacetamide (NBA, 5–50 x 10^-mol/l) showed modified Na⁺ channel activity. By chemical removal of inactivation, repetitive openings with an increased life time and burst-like activity occurred. NBA-modified Na⁺ channels differ in life time and may attain either a slightly (mean open time 3.1±0.2 ms) or a strongly (mean open time 15.2±1.4 ms) prolonged open state. This strongly suggests a heterogeneous population of NBA-modified Na⁺ channels in newborn rat cardiocytes.     

Veratridine blocks voltage-gated potassium current in human T lymphocytes and in mouse neuroblastoma cells

(i) Effects of veratridine on ionic conductances of human peripheral blood T lymphocytes have been investigated using the whole-cell patch-clamp technique, (ii) Veratridine reduces the net outward current evoked by membrane depolarizations. The reduction originates from block of a 4-aminopyridine-sensitive, voltage-gated K⁺ current, (iii) Human T lymphocytes do not appear to express voltage-gated Na⁺ channels, since inward currents are observed neither in control nor in veratridine- and bretylium-exposed lymphocytes. (iv) The effect of veratridine consists of an increase in the rate of decay of the voltage-gated K⁺ current and a reduction of the peak current amplitude. Both effects depend on veratridine concentration. Halfmaximum block occurs at 97 m and the time constant of decay is reduced by 50% at 54 m of veratridine. (v) Possible mechanisms of veratridine action are discussed. The increased rate of K⁺ current decay is most likely due to open channel block. The decrease of current amplitude may involve an additional mechanism. (vi) In cultured mouse neuroblastoma N1E-115 cells, veratridine blocks a component of voltage-gated K⁺ current, in addition to its effect on voltage-gated Na⁺ current. This result shows that the novel effect of veratridine is not confined to lymphocytes.We thank Jacobien Künzel of the Wilhelmina Hospital for Children, Utrecht, for providing the blood samples and Aart de Groot for technical assistance. The research was supported by a fellowship of the Royal Netherlands Academy of Arts and Sciences to M. Oortgiesen.     

The Identification of the Sodium Pump

The identification of the sodium potassium pump as a Na⁺, K⁺-ATPase is described.     

The Identification of the Sodium Pump

The identification of the sodium potassium pump as a Na⁺, K⁺-ATPase is described.     

Potassium Currents in Freshly Dissociated Uterine Myocytes from Nonpregnant and Late-Pregnant Rats

In freshly dissociated uterine myocytes, the outward current is carried by K⁺ through channels highly selective for K⁺. Typically, nonpregnant myocytes have rather noisy K⁺ currents; half of them also have a fast-inactivating transient outward current (I_TO). In contrast, the current records are not noisy in late pregnant myocytes, and I_TO densities are low. The whole-cell I_K of nonpregnant myocytes respond strongly to changes in [Ca²⁺]_o or changes in [Ca²⁺]_i caused by photolysis of caged Ca²⁺ compounds, nitr 5 or DM-nitrophene, but that of late-pregnant myocytes respond weakly or not at all. The Ca²⁺ insensitivity of the latter is present before any exposure to dissociating enzymes. By holding at −80, −40, or 0 mV and digital subtractions, the whole-cell I_K of each type of myocyte can be separated into one noninactivating and two inactivating components with half-inactivation at approximately −61 and −22 mV. The noninactivating components, which consist mainly of iberiotoxin-susceptible large-conductance Ca²⁺-activated K⁺ currents, are half-activated at 39 mV in nonpregnant myocytes, but at 63 mV in late-pregnant myocytes. In detached membrane patches from the latter, identified 139 pS, Ca²⁺-sensitive K⁺ channels also have a half-open probability at 68 mV, and are less sensitive to Ca²⁺ than similar channels in taenia coli myocytes. Ca²⁺-activated K⁺ currents, susceptible to tetraethylammonium, charybdotoxin, and iberiotoxin contribute 30–35% of the total I_K in nonpregnant myocytes, but <20% in late-pregnant myocytes. Dendrotoxin-susceptible, small-conductance delayed rectifier currents are not seen in nonpregnant myocytes, but contribute ∼20% of total I_K in late-pregnant myocytes. Thus, in late-pregnancy, myometrial excitability is increased by changes in K⁺ currents that include a suppression of the I_TO, a redistribution of I_K expression from large-conductance Ca²⁺-activated channels to smaller-conductance delayed rectifier channels, a lowered Ca²⁺ sensitivity, and a positive shift of the activation of some large-conductance Ca²⁺-activated channels.     

Biophysical properties and slow voltage-dependent inactivation of a sustained sodium current in entorhinal cortex layer-II principal neurons: a whole-cell and single-channel study.

The functional and biophysical properties of a sustained, or "persistent," Na(+) current (I(NaP)) responsible for the generation of subthreshold oscillatory activity in entorhinal cortex layer-II principal neurons (the "stellate cells") were investigated with whole-cell, patch-clamp experiments. Both acutely dissociated cells and slices derived from adult rat entorhinal cortex were used. I(NaP), activated by either slow voltage ramps or long-lasting depolarizing pulses, was prominent in both isolated and, especially, in situ neurons. The analysis of the gating properties of the transient Na(+) current (I(NaT)) in the same neurons revealed that the resulting time-independent "window" current (I(NaTW)) had both amplitude and voltage dependence not compatible with those of the observed I(NaP), thus implying the existence of an alternative mechanism of persistent Na(+)-current generation. The tetrodotoxin-sensitive Na(+) currents evoked by slow voltage ramps decreased in amplitude with decreasing ramp slopes, thus suggesting that a time-dependent inactivation was taking place during ramp depolarizations. When ramps were preceded by increasingly positive, long-lasting voltage prepulses, I(NaP) was progressively, and eventually completely, inactivated. The V(1/2) of I(NaP) steady state inactivation was approximately -49 mV. The time dependence of the development of the inactivation was also studied by varying the duration of the inactivating prepulse: time constants ranging from approximately 6.8 to approximately 2.6 s, depending on the voltage level, were revealed. Moreover, the activation and inactivation properties of I(NaP) were such as to generate, within a relatively broad membrane-voltage range, a really persistent window current (I(NaPW)). Significantly, I(NaPW) was maximal at about the same voltage level at which subthreshold oscillations are expressed by the stellate cells. Indeed, at -50 mV, the I(NaPW) was shown to contribute to >80% of the persistent Na(+) current that sustains the subthreshold oscillations, whereas only the remaining part can be attributed to a classical Hodgkin-Huxley I(NaTW). Finally, the single-channel bases of I(NaP) slow inactivation and I(NaPW) generation were investigated in cell-attached experiments. Both phenomena were found to be underlain by repetitive, relatively prolonged late channel openings that appeared to undergo inactivation in a nearly irreversible manner at high depolarization levels (-10 mV), but not at more negative potentials (-40 mV).     

Analytical studies of rapidly inactivating and noninactivating sodium currents in differentiated NG108-15 neuronal cells

The rapidly inactivating (I_Naf) and noninactivating Na⁺ currents (I_Na(NI)) were characterized in NG108-15 neuronal cells differentiated with dibutyryl cyclic AMP in this study. Standard activation and inactivation protocols were used to evaluate the steady-state and kinetic properties of the I_Naf present in these cells. The voltage protocols with a slowly depolarizing ramp were implemented to examine the properties of I_Na(NI). Based on experimental data and computer simulations, a window component of the rapidly inactivating sodium current (I_Naf(W)) was also generated in response to the slowly depolarizing ramp. The I_Naf(W) was subtracted from I_Na(NI) to yield the persistent Na⁺ current (I_Na(P)). Our results demonstrate the presence of I_Na(P) in these cells. In addition to modifying the steady-state inactivation of I_Naf, ranolazine or riluzloe could be effective in blocking I_Naf(W) and I_Na(P). The ability of ranolazine and riluzole to suppress I_Na(P) was greater than their ability to inhibit I_Naf(W). In current-clamp recordings, current-induced voltage oscillations were applied to elicit action potentials (APs) through a gradual transition between spontaneous depolarization and upstroke. Ranolazine or riluzole at a concentration of 3 μM then effectively suppressed the AP firing generated by oscillatory changes in membrane current. The data suggest that a small rise in I_Na(NI) facilitates neuronal hyper-excitability due the decreased threshold of AP initiation. The underlying mechanism of the inhibitory actions of ranolazine or riluzole on membrane potential in neurons or neuroendocrine cells in vivo may thus be associated with their blocking of I_Na(NI).     

Electrogenic sodium-sodium exchange carried out by Na,K-ATPase containing the amino acid substitution Glu779Ala

Na,K-ATPase containing the amino acid substitution glutamate to alanine at position 779 of the alpha subunit (Glu779Ala) supports a high level of Na-ATPase and electrogenic Na+-Na+ exchange activity in the absence of K+. In microsomal preparations of Glu779Ala enzyme, the Na+ concentration for half maximal activation of Na-ATPase activity was 161 +/- 14 mM (n = 3). Furthermore, enzyme activity with 800 mM Na+ was found to be similar in the presence and absence of 20 mM K+. These results showed that Na+, with low affinity, could stimulate enzyme turnover as effectively as K+. To gain further insight into the mechanism of this enzyme activity, HeLa cells expressing Glu779Ala enzyme were voltage clamped with patch electrodes containing 115 mM Na+ during superfusion in K+-free solutions. Electrogenic Na+-Na+ exchange was observed as an ouabain-inhibitable outward current whose amplitude was proportional to extracellular Na+ (Na+(o)) concentration. At all Na+(o) concentrations tested (3-148 mM), exchange current was maximal at negative membrane potentials (V(M)), but decreased as V(M) became more positive. Analyzing this current at each V(M) with a Hill equation showed that Na+-Na+ exchange had a high-affinity, low-capacity component with an apparent Na+(o) affinity at 0 mV (K0(0.5)) of 13.4 +/- 0.6 mM and a low-affinity, high-capacity component with a K0(0.5) of 120 +/- 13 mM (n = 17). Both high- and low-affinity exchange components were V(M) dependent, dissipating 30 +/- 3% and 82 +/- 6% (n = 17) of the membrane dielectric, respectively. The low-affinity, but not the high-affinity exchange component was inhibited with 2 mM free ADP in the patch electrode solution. These results suggest that the high-affinity component of electrogenic Na+-Na+ exchange could be explained by Na+(o) acting as a low-affinity K+ congener; however, the low-affinity component of electrogenic exchange appeared to be due to forward enzyme cycling activated by Na+(o) binding at a Na+-specific site deep in the membrane dielectric. A pseudo six-state model for the Na,K-ATPase was developed to simulate these data and the results of the accompanying paper (Peluffo, R.D., J.M. Argüello, and J.R. Berlin. 2000. J. Gen. Physiol. 116:47-59). This model showed that alterations in the kinetics of extracellular ion-dependent reactions alone could explain the effects of Glu779Ala substitution on the Na,K-ATPase.     

Pivotal Role of Reduced Glutathione in Oxygen-induced Regulation of the Na<Superscript><Emphasis Type="Bold">+</Emphasis></Superscript>/K<Superscript><Emphasis Type="Bold">+</Emphasis></Superscript> Pump in Mouse Erythrocyte Membranes

This study addresses the mechanisms of oxygen-induced regulation of ion transport pathways in mouse erythrocyte, specifically focusing on the role of cellular redox state and ATP levels. Mouse erythrocytes possess Na⁺/K⁺ pump, K⁺-Cl^– and Na⁺-K⁺-2Cl^– cotransporters that have been shown to be potential targets of oxygen. The activity of neither cotransporter changed in response to hypoxia-reoxygenation. In contrast, the Na⁺/K⁺ pump responded to hypoxic treatment with reversible inhibition. Hypoxia-induced inhibition was abolished in Na⁺-loaded cells, revealing no effect of O₂ on the maximal operation rate of the pump. Notably, the inhibitory effect of hypoxia was not followed by changes in cellular ATP levels. Hypoxic exposure did, however, lead to a rapid increase in cellular glutathione (GSH) levels. Decreasing GSH to normoxic levels under hypoxic conditions abolished hypoxia-induced inhibition of the pump. Furthermore, GSH added to the incubation medium was able to mimic hypoxia-induced inhibition. Taken together these data suggest a pivotal role of intracellular GSH in oxygen-induced modulation of the Na⁺/K⁺ pump activity.     

Sodium localization in the choroid plexus

Summary The localization of sodium ion in the cat choroid plexus was studied by use of potassium pyroantimonate. The precipitates formed by the potassium pyroantimonate occur mostly on the plasma membrane in the epithelial cell and occasionally in the perivascular space. The precipitates in the epithelial cell are most numerous at the apical surface, particularly on the microvilli, and least in number at the basal and lateral surfaces. In the endothelial cell, the dense precipitates are situated on the plasma membrane as well as on the limiting membrane of the pinocytotic vesicle. Although the dense precipitates are sometimes situated on the external surface of the plasma membrane of the epithelial cell, most of them are localized on the internal surface of the plasma membrane. A similar localization of the precipitates is to be seen on the plasma membrane of the erythrocyte. When the cerebrospinal fluid/plasma ion ratio and potential gradients across the choroid plexus are considered, the precipitates on the plasma membrane would suggest a localization of sodium needed for the activation of ATPase.

---

Zusammenfassung Die Lokalisation des Natriumions im Plexus chorioideus der Katze wurde mit Hilfe von Kaliumpyroantimonat untersucht. Die durch Kaliumpyroantimonat gebildeten Niederschläge treten meistens an der Plasmamembran in den Epithelzellen und gelegentlich im perivaskulären Raum auf. In den Epithelzellen kommen die Niederschläge am zahlreichsten an der apikalen Oberfläche vor, besonders an den Mikrovilli, am geringsten an den basalen und lateralen Oberflächen. In der Endothelzelle liegen die dichten Niederschläge an der Plasmamembran und an der Grenzmembran der Pinozytosebläschen. Einige der dichten Niederschläge befinden sich an der äußeren Oberfläche der Plasmamembran der Epithelzellen, die meisten aber an der inneren Oberfläche der Plasmamembran. Eine ähnliche Lokalisation der Niedersschläge wurde an der Plasmamembran des Erythrozyten festgestellt. Wenn man das Liquor Plasma-Ionenverhältnis und die Potentialgradienten am Plexus chorioideus in Betracht zieht, liegt es nahe, die nachgewiesene Lokalisation des Natriums auf eine Aktivierung von ATPase zu beziehen.

     

Inhibition of Na(+),K(+)-ATPase activity in hippocampus of rats subjected to acute administration of homocysteine is prevented by vitamins E and C treatment

In the present study we evaluated the effect of acute homocysteine (Hcy) administration on Na⁺,K⁺-ATPase activity, as well as on some parameters of oxidative stress such as total radical-trapping antioxidant potential (TRAP) and on activities of antioxidant enzymes catalase (CAT), superoxide dismutase and glutathione peroxidase in rat hippocampus. Results showed that Hcy significantly decreased TRAP, Na⁺,K⁺-ATPase and CAT activities, without affecting the activities of superoxide dismutase and glutathione peroxidase. We also verified the effect of chronic pretreatment with vitamins E and C on the reduction of TRAP, Na⁺,K⁺-ATPase and CAT activities caused by Hcy. Vitamins E and C per se did not alter these parameters, but prevented the reduction of TRAP, Na⁺,K⁺-ATPase and CAT activities caused by Hcy. Our results indicate that oxidative stress is probably involved in the pathogenesis of homocystinuria and that reduction of Na⁺,K⁺-ATPase activity may be related to the neuronal dysfunction found in homocystinuric patients.     

Juvenile hormone dependent phosphorylation of a 100 kDa polypeptide is mediated by protein kinase C in the follicle cells of Rhodnius prolixus

Summary

The addition of juvenile hormone I (JH I) to membrane preparations of the follicle cells from vitellogenic follicles of the insect Rhodnius prolixus causes a significant increase in the phosphorylation of a 100 kDa polypeptide; and ouabain, a specific inhibitor of Na⁺K⁺-ATPase, eliminates this effect. H-7 (1-(5-isoquinolinesulfonyl)-2-methylpiperazine), an inhibitor of protein kinase C (PKC), also eliminates the JH-dependent phosphorylation of this polypeptide. PDBU (phorbol-12, 13-dibutyrate), an activator of PKC, mimics the action of JH in increasing the phosphorylation of the 100 kDa polypeptide. Because these findings parallel the action of JH in causing the patency, the appearance of large spaces between the follicle cells through which vitellogenin gains access to the oocyte surface, they suggest that phosphorylation of one or more membrane proteins is a key event in the development of patency in response to JH. The 100 kDa polypeptide may represent the a-subunit of Na⁺K⁺-ATPase.     

Role of skeletal muscle Na+-K+ ATPase activity in increased lactate production in sub-acute sepsis

Bacterial sepsis is frequently accompanied by increased blood concentration of lactic acid, which traditionally is attributed to poor tissue perfusion, hypoxia and anaerobic glycolysis. Therapy aimed at improving oxygen delivery to tissues often does not correct the hyperlactatemia, suggesting that high blood lactate in sepsis is not due to hypoxia. Various tissues, including skeletal muscle, demonstrate increased lactate production under well-oxygenated conditions when the activity of the Na+-K+ ATPase is stimulated. Although both muscle Na+-K+ ATPase activity and muscle plasma membrane content of Na+, K+-ATPase subunits are increased in sepsis, no studies in vivo have demonstrated correlation between lactate production and changes in intracellular Na+ and K+ resulting from increased Na+-K+ pump activity in sepsis. Plasma concentrations of lactate and epinephrine, a known stimulator of the Na+-K+ pump, were increased in rats made septic by E. coli injection. Muscle lactate content was significantly increased in septic rats, although muscle ATP and phosphocreatine remained normal, suggesting oxygen delivery remained adequate for mitochondrial energy metabolism. In septic rats, muscle intracellular ratio of Na+:K+ was significantly reduced, indicating increased Na+-K+ pump activity. These data thus demonstrate that increased muscle lactate during sepsis correlates with evidence of elevated muscle Na+-K+ ATPase activity, but not with evidence of impaired oxidative metabolism. This study also further supports a role for epinephrine in this process.     

Capsaicin inhibits intestinal Cl- secretion and promotes Na+ absorption by blocking TRPV4 channels in healthy and colitic mice

Although capsaicin has been studied extensively as an activator of the transient receptor potential vanilloid cation channel subtype 1 (TRPV1) channels in sensory neurons, little is known about its TRPV1-independent actions in gastrointestinal health and disease. Here, we aimed to investigate the pharmacological actions of capsaicin as a food additive and medication on intestinal ion transporters in mouse models of ulcerative colitis (UC). The short-circuit current (I_sc) of the intestine from WT, TRPV1-, and TRPV4-KO mice were measured in Ussing chambers, and Ca²⁺ imaging was performed on small intestinal epithelial cells. We also performed Western blots, immunohistochemistry, and immunofluorescence on intestinal epithelial cells and on intestinal tissues following UC induction with dextran sodium sulfate. We found that capsaicin did not affect basal intestinal I_sc but significantly inhibited carbachol- and caffeine-induced intestinal I_sc in WT mice. Capsaicin similarly inhibited the intestinal I_sc in TRPV1 KO mice, but this inhibition was absent in TRPV4 KO mice. We also determined that Ca²⁺ influx via TRPV4 was required for cholinergic signaling–mediated intestinal anion secretion, which was inhibited by capsaicin. Moreover, the glucose-induced jejunal I_scvia Na⁺/glucose cotransporter was suppressed by TRPV4 activation, which could be relieved by capsaicin. Capsaicin also stimulated ouabain- and amiloride-sensitive colonic I_sc. Finally, we found that dietary capsaicin ameliorated the UC phenotype, suppressed hyperaction of TRPV4 channels, and rescued the reduced ouabain- and amiloride-sensitive I_sc. We therefore conclude that capsaicin inhibits intestinal Cl^- secretion and promotes Na⁺ absorption predominantly by blocking TRPV4 channels to exert its beneficial anti-colitic action.