Muscle Of Guinea-pig Ileum Research Articles

Molecular mechanism of the effects of guanine nucleotide and sulfhydryl reagent on muscarinic receptors in smooth muscles studied by radiation inactivation

The molecular sizes of the units concerned in 3-quinuclidinyl benzilate (QNB) binding and in the effects of guanine nucleotide and sulfhydryl reagent on the inhibition of QNB binding by carbachol in smooth muscle of guinea pig ileum were determined to be 76,000, 179,000 and 107,000, respectively by the radiation inactivation method. One or more subunits (GTP subunit) other than the receptor subunit in a muscarinic receptor appeared to be involved in the effect of guanine nucleotide. When guanine nucleotide was present, the receptor subunit seemed to be dissociated from the GTP subunit.

β-endorphin proteolysis by guinea-pig ileum myenteric plexus membranes: Increased γ-endorphin turnover after chronic exposure to morphine

The influence of chronic morphine exposure in vitro on the biotransformation of β-endorphin (βE) was investigated using the myenteric plexus-longitudinal muscle of guinea-pig ileum. A membrane preparation was incubated with βE and the degradation of βE as well as the accumulation of several βE fragments in the incubation medium were followed with time. The levels of peptides were determined by specific radioimmunoassays after separation by high-pressure liquid chromatography. It was found that exposure to morphine did not affect the disappearance of βE, but altered the time course of accumulation of βE fragments. In fact, the accumulation of γ-endorphin, α-endorphin and des-tyrosine 1-α-endorphin was enhanced, while that of des-tyrosine 1-γ-endorphin was not changed. Additionally, the disappearance of γ-endorphin appeared to be stimulated by morphine exposure. These data provide evidence that the fragmentation of βE is changed by chronic morphine exposure in such a way that the turn-over of γ-endorphin is increased.

Reversible inhibition of acetylcholinesterase by eseroline, an opioid agonist structurally related to physostigmine (eserine) and morphine

The action of eseroline—(3 aS, 8 aR)-1,2,3,3 a,8,8 a-hexahydro-1,3 a,8-trimethylpyrrolo[2,3- b] indol-5-ol—salicylate was tested on preparations of ChE from different sources and on the longitudinal muscle of guinea-pig ileum. While eseroline is extremely weak-acting on horse serum BuChE ( K i = 208 ± 42 μM), it is a rather strong competitive inhibitor of AChE's, its K i being 0.15 ± 0.08 μM, 0.22 ± 0.10 μM and 0.61 ± 0.12 μM in electric eel, human RBC and rat brain, respectively. Eseroline inhibitory action on AChE is independent of the duration of pre-incubation and appears fully developed in less than 15 sec. This action is also rapidly reversible; after pre-incubation followed by dilution, maximum enzymic activity is regained within 15 sec. The electrically-evoked contractions of the longitudinal strip were inhibited by concentrations of eseroline in the range 0.2–15 μM, while they were increased by concentrations over 20 μM. In the same preparation, without electrical stimulation, but in the presence of naloxone, eseroline induced contractions at concentrations higher than 5 μM. This effect was antagonized by atropine. The inhibitory activity of eseroline parallels, as regards selectivity, potency and kinetics, that of the phenolic anticurare agent edrophonium, while it differs markedly from that of physostigmine.

Depolarization-induced release of adenosine 5'-triphosphate from isolated varicosities derived from the myenteric plexus of the guinea pig small intestine

In order to study the release of ATP from a neuronal preparation thought to be "purinergic," isolated varicosities were prepared from myenteric plexus by mincing and homogenizing the longitudinal muscle of guinea pig ileum in 0.32 M sucrose. The presence of varicosities within the crude preparation (P2), isolated by differential centrifugation, was confirmed by electron microscopy and by the presence of occluded lactate dehydrogenase as a cytoplasmic marker. Varicosities were purified further from the P2 fraction on a discontinuous sucrose density gradient and characterized morphologically. Varicosities resembling cholinergic, "purinergic," and adrenergic axonal terminals were identified. The release of ATP from both crude and purified varicosities was detected by monitoring the light produced when the released ATP reacted with firefly luciferin-luciferase which was present in the incubation medium. Elevated extracellular K+ or Rb+ caused the release of ATP, whereas elevated Na+ and Li+ did not. The release of ATP by either K+ or by the depolarizing drug, veratridine, was Ca2+ dependent. This requirement of extracellular Ca2+ for veratridine-induced release of ATP from isolated myenteric varicosities contrasted strikingly with that for brain synaptosomes, where the release of ATP induced by veratridine was increased rather than decreased in a Ca2+-free medium. The characteristics of ATP release from myenteric varicosities are consistent with a possible neurotransmitter function for ATP in myenteric plexus, although it is also possible that ATP is co-released with some other neurotransmitter.

Differentiation of Ca 2+ pumps linked to plasma membrane and endoplasmic reticulum in the microsomal fraction from intestinal smooth muscle

ATP promotes 45Ca uptake by the microsomal fraction from the longitudinal smooth muscle of guinea-pig ileum and this uptake is stimulated by oxalate. As the microsomal fraction is made up of various subcellular entities, we examined the localization of the Ca 2+-transport activity by density gradient centrifugation, taking advantage of the selective effect of digitonin (at low concentration) on the density of plasmalemmal elements. When the 45Ca-uptake activity was measured in the absence of oxalate, its behavior in subfractionation experiments closely paralleled that of the plasmalemmal marker 5′-nucleotidase. In contrast, the additional Ca 2+-transport activity elicited by oxalate behaved like NADH-cytochrome c reductase, a putative endoplasmic reticulum marker. The endoplasmic reticulum vesicles constituted only a small part of the membranes in the microsomal fraction, which explains that their Ca 2+-storage capacity was not detectable in the absence of Ca 2+-trapping agent. Low digitonin concentrations selectively increased the Ca 2+ permeability of the plasmalemmal vesicles. The two Ca 2+-transport activities were further differentiated by their distinct sensitivities to K +, vanadate and calmodulin. In this respect, the oxalte-insensitive and oxalate-stimulated Ca 2+-transport systems resembled, respectively, the sarcolemmal and sarcoplasmic reticulum Ca 2+ pumps in cardiac and skeletal muscle, in accordance with the subcellular locations established by density gradient centrifugation.

Evidence that histamine and carbachol may open the same ion channels in longitudinal smooth muscle of guinea-pig ileum.

1. Membrane potential was recorded intracellularly by micro-electrode in separated longitudinal muscle of guinea-pig ileum. Electrotonic potentials were evoked in longitudinal strips by passing current between large external electrodes in the partition chamber.2. Histamine increased the frequency of action potential discharge at low concentrations and depolarized the membrane. At higher concentrations it caused substantial depolarization and action potential discharge was abolished. Carbachol had similar actions but the maximal depolarization by carbachol (using 10(-4)m) was some 4-5 mV greater than maximal depolarization by histamine (using 10(-4)m).3. The change in size of evoked electrotonic potentials was used to estimate the effects of carbachol and histamine on the conductance of the smooth muscle membrane. The equilibrium potentials for histamine and carbachol depolarizations were estimated from their relative effects on potential and conductance and were found to be not significantly different; measurements of the effects on conductance showed that 10(-4)m-histamine increased conductance about 8-fold whilst 10(-4)m-carbachol had a much greater effect on conductance. This difference could explain the differing maximal depolarizing effects of these agents if both were assumed to open channels having the same ionic selectivity (i.e. equilibrium potential).4. The efflux of (42)K was studied in separated strips of longitudinal ileal muscle from guinea-pig. In the presence of a concentration of carbachol (2 x 10(-5)m or 10(-4)m) having a maximal effect on (42)K efflux rate, histamine (10(-4)m) did not increase efflux further although 120 mm-potassium did so. Experiments with the irreversible muscarinic receptor blocker, propylbenzilylcholine mustard, indicated that the number of muscarinic receptors did not limit the (42)K efflux response to carbachol and it was suggested that the response was limited by the availability of ion channels which could be opened by activated muscarinic receptors.5. Contractions to histamine and carbachol in 120 mm-potassium depolarizing solution were followed upon washing by a relaxation below basal tension. Carbachol, but not histamine, showed a pronounced and long lasting secondary contraction following this relaxation.6. These results are consistent with the idea that activated histamine and activated muscarinic receptors open the same ion channels in the smooth muscle membrane to produce depolarization, increased action potential discharge and contraction, although muscarinic receptors can open more of these. However, there was evidence that the opening of these channels is not the only pathway between receptor activation and contraction.

New light on the mechanism of action of disodium cromoglycate.

Disodium cromoglycate (DSCG) shows a prolonged protective effect against histamine on the smooth muscle of guinea pig ileum. Preventing allergen-induced mediator release from mast cells as well as protection of smooth muscle against mediators already released can both explain a beneficial effect of DSCG in the treatment of bronchial asthma and food allergy. It is believed that disappointing clinical trials with many new anti-allergic drugs, e.g. RS 7540, can be explained by the lack of protective effect on the smooth muscle of target organs.

ACTIONS OF VARIOUS MUSCARINIC AGONISTS ON MEMBRANE POTENTIAL, POTASSIUM EFFLUX, AND CONTRACTION OF LONGITUDINAL MUSCLE OF GUINEA‐PIG INTESTINE

1 Depolarizations were recorded intracellularly in smooth muscle from the taenia of the guinea-pig caecum in response to the iontophoretic application of acetylcholine, carbachol, oxotremorine-M, methylfurmethide, hexyl trimethylammonium and tetramethylammonium (TMA). 2 No differences between the iontophoretic responses to agonists stable to cholinesterase were detected. 3 The latency and time to peak of acetylcholine-induced depolarizations were less than those to stable agonists, and the response was briefer and less complex in shape. These differences were reduced, or disappeared, upon inhibition of cholinesterase. 4 The rate of loss of 42K and changes in length were measured in superfused strips weighing about 10 mg of separated longitudinal muscle of guinea-pig ileum. 5 Acetylcholine, carbachol, methylfurmethide, butyltrimethylammonium and TMA contracted the muscle and increased the rate of loss of 42K. 6 Contrary to previous reports, no evidence of a selective action of any of these agonists on 42K loss was detected. TMA appeared to be a partial agonist in evoking 42K loss, although it produced a maximum contraction. 7 The maximum 42K efflux produced by acetylcholine was about 40% of the maximum evoked by application of carbachol or methylfurmethide. If cholinesterase was inhibited, the 42K efflux evoked by maximally effective concentrations of acetylcholine was comparable to that evoked by a stable agonist. 8 These results are consistent with the idea that the muscarinic agonists used interact in an essentially similar way with muscarinic receptors to produce their effects on membrane potential, permeability, and tension.

Evidence that the action of cholecystokinin octapeptide on the guinea pig ileum longitudinal muscle is mediated in part by substance P release from the myenteric plexus

Studies were made on the mode of action of cholecystokinin octapeptide (CCK8) on longitudinal muscle strips of guinea pig ileum in vitro. CCK8 produced dose-related contractions of innervated strips of ileum longitudinal muscle (EC 50 3–4 × 10 −9 M), but was inactive on denervated strips. Tetrodotoxin, and reducing the bath temperature to 15°C, abolished the response of innervated strips to CCK8. These results indicate that the action of CCK8 on ileal longitudinal muscle is mediated by the myenteric plexus. Atropine abolished the responses to acetylcholine and to low doses of CCK8. However, the responses to CCK8 in doses above 10 −8 M were reduced by atropine but not abolished. Incubation of longitudinal muscle strips with high concentrations of substance P (1.5 × 10 −7 M) resulted in desensitization to this peptide; this treatment inhibited the responses to CCK8 alone and abolished the atropine-resistant actions of CCK8. Disensitization to substance P had no effect on the responses to acetylcholine, histamine, serotonin and angiotensin II. The results indicate that CCK8 contracts the longitudinal muscle of guinea pig ileum by releasing acetylcholine and substance P from the myenteric plexus.

Stimulation of phosphatidylinositol turnover in various tissues by cholinergic and adrenergic agonists, by histamine and by caerulein.

Studies are reported of the biochemical and pharmacological characteristics of the stimulation of phosphatidylinositol metabolism that is produced in appropriate target tissues by stimulation of various receptors that use Ca(2+) as their second messenger. (1) Muscarinic cholinergic and alpha-adrenergic phosphatidylinositol responses were observed in rat lacrimal gland, and a response to caerulein was detected in the longitudinal smooth muscle of guinea-pig ileum. (2) The muscarinic cholinergic phosphatidylinositol response of rat lacrimal gland, like that of several other tissues, is not dependent on the availability of extracellular Ca(2+). (3) Three phosphatidylinositol responses, namely to histamine in guinea-pig ileum smooth muscle, to alpha-adrenergic stimulation in rat vas deferens and to muscarinic cholinergic stimulation in rat lacrimal gland, were all found to involve phosphatidylinositol breakdown. (4) The stereospecificity of the muscarinic receptor responsible for the phosphatidylinositol response of guinea-pig pancreas was tested by using the two stereoisomeric forms of acetyl-beta-methylcholine; the S-isomer was very much more active than the R-isomer in provoking both phosphatidylinositol breakdown and its labelling with (32)P, as it is in provoking other physiological responses such as contractility or secretion. (5) Pilocarpine, a muscarinic partial agonist, provoked a significantly smaller phosphatidylinositol breakdown in rat parotid fragments than did carbamoylcholine, a potent muscarinic agonist. (6) All of these results are consistent with, but do not prove, a previously offered hypothesis that suggests that phosphatidylinositol breakdown is a reaction essential to stimulus-response coupling at a variety of cell-surface receptors that mobilize Ca(2+) from and through the plasma membranes of target tissues.

Effect of prostaglandin E 1 and indomethacin on responses of longitudinal muscle of guinea-pig ileum to cholecystokinin

The effect of prostaglandin E 1 (PGE 1) and indomethacin (IND) cholecystokinin (CCK)-induced contractions of guinea-pig isolated ileum longitudinal muscle were studied. PGE 1 (2.8–28 nM) consistently and dose dependently increased the contractions evoked by CCK (indirect muscle stimulation) or by ACh. IND (2.7μM) decreased the contractions to both compounds and this was reversed with 2.8–7 nM PGE 1. Pretreatment of the preparations with phentolamine (2.6μM) or pretreatment of the animals with reserpine (2 mg/kg i.p. 24 h before killing) did not affect PGE 1 potentiation or IND inhibition of CCK-induced contractions. The results indicated that PGE 1 potentiated CCK-induced contractions of the longitudinal muscle of guinea-pig ileum by increasing the response to released ACh. Experiments with IND suggested that endogenous PGs may modulate the effect of CCK or related gastrointestinal hormones.

Antagonistic effect of compound 48/80 on the inhibitory actions of morphine and methionine-enkephalin on electrically-induced contractions of the guinea-pig ileum.

1 The effect of compound 48/80 was studied on the twitch-like contractions of the longitudinal muscle of guinea-pig ileum induced by electrical stimulation of intramural cholinergic nerves. 2 Compound 48/80 alone, at concentrations up to 30 microgram/ml, had no effect on the twitch contractions. The contraction to exogenously applied acetylcholine was slightly depressed by the compound. 3 At 100 microgram/ml, compound 48/80 caused a weak but long-lasting increase in tone and irregular contractile activity in the ileum, part of which was reduced but not completely abolished by pretreatment with chlorpheniramine (1 muM) or by repeated applications of compound 48/80. 4 The inhibitory effects of morphine and methionine-enkephalin on the twitches were antagonized by the presence of compound 48/80 (3 to 30 microgram/ml), possibly in a competitive manner. The antagonism was not affected by pretreatment with the antihistaminics, chlorpheniramine and/or metiamide. 5 The inhibitory effects of noradrenaline and adrenaline on the twitches were slightly but significantly increased by the presence of compound 48/80 (10 or 30 microgram/ml), whereas that of ATP was not modified. 6 Thesese results indicate that compound 48/80 acts as a selective and competitive antagonist at opiate receptors located in the intramural cholinergic nerves of guinea-pig ileum.

THE EFFECT OF MAGNESIUM ON THE RESPONSE OF SMOOTH MUSCLE TO 5‐HYDROXYTRYPTAMINE

1 The responses to 5-hydroxytryptamine (5-HT) of rabbit isolated mesenteric artery and vein and longitudinal smooth muscle of guinea-pig ileum were examined in Krebs solution containing 0, 1.2 or 2.4 mM Mg2+. 2 When the concentration of Mg2+ was raised the spontaneous contractile activity of rabbit mesenteric vein was depressed. The responses to 5-HT in rabbit mesenteric artery and vein and guinea-pig ileum were greater in the absence of Mg2+. The initial fast component of 5-HT-induced contractions in rabbit mesenteric vein was reduced more consistently than the subsequent slow component by increasing the Mg2+ concentration. 3 Exposure of mesenteric vein to Ca-free solution containing ethyleneglycoltetra-acetic acid (EGTA) promptly abolished 5-HT contraction in normal-Mg but not in low-Mg Krebs solution. 4 In mesenteric veins, no difference was observed in either the 'lanthanum-resistant' uptake of 45Ca or total tissue Ca, measured by atomic absorption spectrophotometry, after 60 min exposure to either low-Mg or normal-Mg Krebs solution. On the other hand, after 5 min exposure, the 'lanthanum-resistant' uptake of 45Ca was greater in the absence of Mg2+ than in the presence of higher Mg2+ concentrations. 5 It is suggested that Mg2+ depressed the 5-HT response at least partly by reducing the availability of Ca2+ from a rapidly equilibrating intracellular pool.

Release of 3H-acetylcholine from isolated guinea pig ileum. A radiochemical method for studying the release on the cholinergic neurotransmitter in the intestine.

Innervated strips of longitudinal muscle of guinea pig ileum were incubated with 3H-choline in the presence of physostigmine, after which the efflux of tritiated metabolites was studied. Under resting conditions 3H-acetylcholine, 3H-choline and other tritiated metabolites were released into the incubation medium. Analysis of the kinetics of the release of the metabolites indicated that the release occurred from at least 2 different compartments. Under the unstimulated conditions used, between 72 and 78% of the radio-activity remained in a third, non-releasable compartment. The release of 3H-acetylcholine showed spontaneous fluctuations which were positively correlated to spontaneous variations of the isometric tension of the preparation. Electrical field stimulation at low frequency (0.5 Hz) consistently increased the release of 3H-acetylcholine. The release of 3H-choline was increased only slightly or not at all by the electrical stimulation. For studying stimulation-evoked release of 3H-acetylcholine, it is suggested that the measurement of the total quaternary amine release is of similar value to measurement of 3H-acetylcholine itself. This approach considerably simplified the method. During 5 consecutive stimulation periods of 150 pulses each, the increase in the release of total quaternary amines diminished with time. By taking into account the reduction of the stores of radioactivity in the tissue during the experiment, correction for the negative trend could be made. When the preparation was stimulated with between 30 and 3000 pulses a close correlation was found between the increase in the release of total quaternary amines and the number of pulses delivered. The volley output of the quaternary amines was not constant, however, but diminished by increasing stimulation frequency.

238) - Effect of compound 48/80 on the twitch contraction caused by electrical stimulation of the longitudinal muscle of guinea pig ileum

238) - Effect of compound 48/80 on the twitch contraction caused by electrical stimulation of the longitudinal muscle of guinea pig ileum

Effects of calcium-antagonistic drugs on the stimulation by carbamoylcholine and histamine of phosphatidylinositol turnover in longitudinal smooth muscle of guinea-pig ileum.

A number of drugs classed as calcium antagonists, spasmolytics, non-specific receptor antagonists or receptor antagonists with multiple sites of action were tested to determine whether they prevent the stimulation of phosphatidylinositol turnover caused in various tissues by the activation of receptors which increase cell-surface Ca2+ permeability. The experiments were done with fragments of longitudinal smooth muscle from guinea-pig ileum; these were incubated in vitro with 32Pi and either 100 muM-carbamoylcholine or 100 muM-histamine, in the presence of antagonistic drugs at concentrations at least sufficient to cause complete blockade of smooth-muscle contraction. The phosphatidylinositol response to carbamoylcholine was not changed by cinchocaine, papaverine, nifedipine, dibenamine, amethocaine, cinnarizine, lidoflazine, methoxyverapamil, prenylamine or two antimuscarinic alkane-bis-ammonium compounds, and the response to histamine was unaffected by the first four drugs. In contrast, phenoxybenzamine prevented the increase in phosphatidylinositol labelling caused by either carbamoylcholine or histamine. The insensitivity of the phosphatidylinositol response to most of the drugs provides further experimental support for the conclusion that the receptor-stimulated phosphatidylinositol breakdown which initiates the increase in phosphatidylinositol turnover is not caused by an increase in intracellular Ca2+. The simplest interpretation of the available information appears to be that phosphatidylinositol breakdown plays a role in the coupling between the receptor-agonist interaction and the opening of cell-surface Ca2+ gates [Michell, R. H. (1975) Biochim. Biophys. Acta 415, 81-147]. If this is correct, then phenoxybenzamine must exert its inhibitory effects on phosphatidylinositol breakdown early in this sequence of events, but the drugs must act at a stage later than phosphatidylinositol breakdown. The unexpected difference in the effects of dibenamine and phenoxybenzamine, which are chemically very similar, may provide a useful experimental tool with which to explore the way in which activated receptors provoke the opening of cell-surface Ca2+ gates.

Stimulation of phosphatidylinositol turnover by histamine, 5-hydroxytryptamine and adrenaline in the longitudinal smooth muscle of guinea pig ileum

Stimulation of phosphatidylinositol turnover by histamine, 5-hydroxytryptamine and adrenaline in the longitudinal smooth muscle of guinea pig ileum

Conformational changes at membranes of target cells induced by the peptide hormone angiotensin. A spin label study

FEBS LettersVolume 47, Issue 1 p. 193-196 Full-length articleFree Access Conformational changes at membranes of target cells induced by the peptide hormone angiotensin. A spin label study S. Schreier-Muccillo, S. Schreier-Muccillo Institute of Chemistry, University of São Paulo, Department of Biochemistry, Faculdade de Medicina da Santa Casa, and Department of Biophysics, Escola Paulista de Medicina, São Paulo, BrazilSearch for more papers by this authorG.X. Niculitcheff, G.X. Niculitcheff Institute of Chemistry, University of São Paulo, Department of Biochemistry, Faculdade de Medicina da Santa Casa, and Department of Biophysics, Escola Paulista de Medicina, São Paulo, BrazilSearch for more papers by this authorM.M. Oliveira, M.M. Oliveira Institute of Chemistry, University of São Paulo, Department of Biochemistry, Faculdade de Medicina da Santa Casa, and Department of Biophysics, Escola Paulista de Medicina, São Paulo, BrazilSearch for more papers by this authorS. Shimuta, S. Shimuta Institute of Chemistry, University of São Paulo, Department of Biochemistry, Faculdade de Medicina da Santa Casa, and Department of Biophysics, Escola Paulista de Medicina, São Paulo, BrazilSearch for more papers by this authorA.C.M. Paiva, A.C.M. Paiva Institute of Chemistry, University of São Paulo, Department of Biochemistry, Faculdade de Medicina da Santa Casa, and Department of Biophysics, Escola Paulista de Medicina, São Paulo, BrazilSearch for more papers by this author S. Schreier-Muccillo, S. Schreier-Muccillo Institute of Chemistry, University of São Paulo, Department of Biochemistry, Faculdade de Medicina da Santa Casa, and Department of Biophysics, Escola Paulista de Medicina, São Paulo, BrazilSearch for more papers by this authorG.X. Niculitcheff, G.X. Niculitcheff Institute of Chemistry, University of São Paulo, Department of Biochemistry, Faculdade de Medicina da Santa Casa, and Department of Biophysics, Escola Paulista de Medicina, São Paulo, BrazilSearch for more papers by this authorM.M. Oliveira, M.M. Oliveira Institute of Chemistry, University of São Paulo, Department of Biochemistry, Faculdade de Medicina da Santa Casa, and Department of Biophysics, Escola Paulista de Medicina, São Paulo, BrazilSearch for more papers by this authorS. Shimuta, S. Shimuta Institute of Chemistry, University of São Paulo, Department of Biochemistry, Faculdade de Medicina da Santa Casa, and Department of Biophysics, Escola Paulista de Medicina, São Paulo, BrazilSearch for more papers by this authorA.C.M. Paiva, A.C.M. Paiva Institute of Chemistry, University of São Paulo, Department of Biochemistry, Faculdade de Medicina da Santa Casa, and Department of Biophysics, Escola Paulista de Medicina, São Paulo, BrazilSearch for more papers by this author First published: October 01, 1974 https://doi.org/10.1016/0014-5793(74)80457-6Citations: 7 Supported by grants from FAPESP and CNPq. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume47, Issue1October 01, 1974Pages 193-196 ReferencesRelatedInformation

Interaction of benzilylcholine mustard, benzilylcholine and lachesine with the histamine receptor in the longitudinal muscle of guinea-pig ileum.

1. The histamine receptors of longitudinal muscle strips from guinea-pig ileum were inactivated on extended exposure to concentrations of benzilylcholine mustard (BCM) above 10(-6)M. These concentrations are 3 orders of magnitude greater than those required for inactivation of the muscarinic receptors. Mepyramine (3 x 10(-8)M) afforded complete protection for the histamine receptor against the effects of BCM.2. Recovery from block at 30 degrees C was very slow with a first-order rate constant of approximately 10(-7) s(-1).3. The rate constant, k(2), for the alkylation reaction in which the reversible BCM-receptor complex is converted into an irreversible complex is much greater than the rate constant, k(-1), for dissociation of the reversible complex. The value of the rate constant, k(1), for formation of the reversible complex was 1.1 +/- 0.2 x 10(3)M(-1) s(-1).4. These observations suggested that k(1) was probably not much greater than for BCM acting on the muscarinic receptor, even though the value of k(1) was reduced by more than 2 orders of magnitude. This effect has been established for benzilylcholine and lachesine, reversible analogues of BCM. For both drugs k(1) for the histamine receptor was approximately 3 orders of magnitude less than for the muscarinic receptor, whereas k(1) was greater by a factor of only 6.

Action of acetylcholine on the longitudinal muscle of guinea-pig ileum: the role of an electrogenic sodium pump.

Intracellular recordings of membrane potential were made from the longitudinal muscle of guinea-pig terminal ileum. It was observed that ouabain or potassium-free solution depolarized the membrane. Upon readmitting potassium to potassium-free solution, the membrane potential rapidly increased. This response was blocked by ouabain and was potentiated in chloride-deficient solution, suggesting that it was due to the activity of an electrogenic sodium pump. When acetylcholine was applied, and then washed from the tissue, there followed a period of increased negativity of the membrane potential, an after-hyperpolarization. This did not occur when responses to acetylcholine were obtained in the presence of ouabain, in potassium-free solution, or in sodium-deficient solution, but the after-hyperpolarization was increased in size in chloride-deficient solution. During a 2 min application of carbachol, the membrane potential fell more rapidly in the presence of ouabain (10 -5 mol/1); this could be explained if sodium pump activity is important in retarding the decline of the sodium and potassium gradients that occurs at this time. It was concluded that the application of acetylcholine or carbachol to ileal muscle increases internal sodium and probably external potassium concentrations. These increases stimulate the activity of the electrogenic sodium pump so that, when the membrane resistance recovers, there is an increased electrogenic contribution to the membrane potential. This produces the after-hyperpolarization which is a feature of the response to acetylcholine.