Inhibition by amiloride of contractile elements in smooth muscle of guinea pig taenia cecum and chicken gizzard

The relaxant action of amiloride was investigated in the smooth muscles of guinea pig taenia ceci and chicken gizzard. Amiloride inhibited the contractions induced by high K+ (45.4 mM) and carbachol (10 microM) in the taenia with the concentrations needed to induce 50% inhibition (IC50) of approximately 41 microM. A prolonged incubation period (greater than 1 hr) was necessary to obtain the full inhibition of these contractions. The taenia gradually accumulated amiloride and the tissue/medium ratio exceeded 2.0 after a 120-min incubation period. Amiloride had no effect on the high K+-stimulated 45Ca++ uptake or the ATP content of the taenia. Amiloride inhibited the Ca++-induced contraction of the saponin-treated taenia with an IC50 of 186 microM. Amiloride (10-1000 microM) also inhibited superprecipitation and Mg++-adenosine triphosphatase activity of the gizzard native actomyosin as well as the phosphorylation of myosin light chain. The inhibition of the phosphorylation was antagonized competitively by ATP. Amiloride (1 mM) had no effect on the dephosphorylation of myosin light chain upon removal of Ca++ from reaction medium. Amiloride, at concentrations up to 1 mM, had not effect on calmodulin activity as monitored by the Ca++-calmodulin-activated erythrocyte membrane (Ca++ + Mg++)-adenosine triphosphatase and phosphodiesterase activities. In contrast to this, trifluoperazine inhibited the calmodulin activity at the concentration needed to inhibit the Ca++-induced contraction of the permeabilized taenia and the superprecipitation and the phosphorylation of myosin light chain of gizzard. We conclude that amiloride, unlike trifluoperazine, may inhibit directly the myosin light chain kinase activity to induce muscle relaxation.     

Platelet-activating factor-acether-induced relaxation of guinea pig airway muscle: role of prostaglandin E2 and the epithelium

A fixed concentration of paf-acether (platelet-activating factor; 4 microM) relaxed isolated guinea pig tracheal preparations which had been contracted with histamine (50 microM), serotonin (1 microM) or leukotriene D4 (0.1 microM). The relaxations were approximately 43, 100 and 57%, respectively. We did not observe any relaxant effect of paf-acether (4 microM) in tissues contracted with acetylcholine (50 microM). Both lyso paf-acether (10 microM) and bovine serum albumin (25 micrograms/ml) were without effect on histamine-contracted preparations. In the presence of indomethacin (1.7 microM; 30 min) or aspirin (0.1 mM; 30 min) the relaxant effect of paf-acether (4 microM) in tissues contracted with histamine was significantly reduced to approximately 10 and 12%, respectively. When paf-acether (4 microM) was added to histamine-contracted tracheal preparations in the presence of noradrenaline (0.1 microM) or prostaglandin E2 (PGE2, 10 nM) the relaxations were 62 and 82%, respectively. Noradrenaline and PGE2 alone had only a slight relaxant effect in these tissues (7 and 14%, respectively). In the presence of indomethacin (1.7 microM) the synergistic effect of paf-acether and PGE2 was still observed. The basal production of PGE2 in isolated guinea pig tracheal preparations was 4.6 +/- 1.4 pg/mg of tissue. In the presence of paf-acether (4 microM) increased levels of this prostanoid were detected (11.2 +/- 2.4 pg/mg of tissue). Isolated guinea pig tracheal preparations when contracted with histamine released PGE2 (17.6 +/- 4.1 pg/mg of tissue). In the presence of histamine and paf-acether there was a significant increase in detectable levels of PGE2 (48.6 +/- 13.2 pg/mg of tissue).(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in smooth muscle tone during osmotic challenge in relation to epithelial bioelectric events in guinea pig isolated trachea

The relationship between epithelial bioelectric events and epithelium-dependent relaxant and contractile responses of airway smooth muscle in response to hyperosmolar and hypo-osmolar solutions was investigated in guinea pig isolated trachea. Tracheae were perfused with normal or nonisosmotic modified Krebs-Henseleit solution while simultaneously monitoring transepithelial potential difference (VT) and contractile and relaxant responses of the muscle. Baseline VT was -10.1 to -13.3 mV (distal and proximal ends, respectively). Intraluminal amiloride (10(-4) M) induced a 3.7-mV depolarization, verifying that the VT was of epithelial origin. Extraluminal methacholine (3 x 10(-7) M; EC50) caused hyperpolarization and smooth muscle contraction; intraluminal methacholine had very little effect. Increasing intraluminal bath osmolarity via addition of 240 mOsM NaCl or KCl caused an immediate and prolonged depolarization and epithelium-dependent relaxation. Increasing intraluminal bath osmolarity with sucrose evoked similar responses, except that an immediate, transient hyperpolarization and contraction preceded the depolarization and relaxation. Increasing extraluminal bath osmolarity with 240 mOsM NaCl induced depolarization and a longer lasting epithelium-dependent relaxation, whereas extraluminally added 240 mOsM KCl induced a complex smooth muscle response (i.e., transient relaxation followed by contraction), which was accompanied by prolonged depolarization. Intraluminal hypo-osmolarity produced a transient hyperpolarization followed by depolarization along with contraction of the smooth muscle. Bioelectric responses always preceded smooth muscle responses. These results suggest that bioelectric events in the epithelium triggered by nonisosmotic solutions are associated with epithelium-dependent responses in tracheal smooth muscle.     

Effect of removal of epithelium on antigen-induced smooth muscle contraction and mediator release from guinea pig isolated trachea

We examined the effect of removal of the epithelium on antigen-induced smooth muscle contraction and the release of mediators of inflammation from superfused, sensitized guinea-pig tracheal spirals in vitro. The epithelium was stripped from one-half of each trachea by mechanical means, and immunologic responses were evaluated by paired analysis. Removing the epithelium potentiated antigen-induced contraction, as reflected by a 5-fold leftward shift in the antigen dose-response curve, but the maximum response to antigen was not altered. This potentiation was not inhibited by pretreating the tissues with indomethacin (5 X 10(-6) M). At maximum concentrations of antigen removing the epithelium had no effect on the magnitude or kinetics of release of immunoreactive sulfidopeptide leukotrienes, prostaglandin (PG) D2, PGF2 alpha or thromboxane B2. Removing the epithelium did, however, significantly decrease the release of PGE and 6-keto-PGF1 alpha, a prostacyclin metabolite. Antigen-induced histamine release was enhanced by removing the epithelium; this effect varied inversely with antigen concentration. Selectively exposing either the luminal or serosal surface of an intact, superfused trachea to antigen resulted in the release of less than 5% of the total tissue histamine. Removing the epithelium from the intact trachea increased histamine release to approximately 25% following luminal but not serosal exposure to antigen. These studies demonstrate that the tracheal epithelium can act to inhibit antigen-induced airway contraction in vitro. This may in part reflect the role of the intact epithelium as a diffusion barrier which can limit the rate of influx of antigen molecules and thereby influence tissue mast cell activation.     

Characterization of the contractile serotonergic receptor in guinea pig trachea with agonists and antagonists.

5-Hydroxytryptamine (5-HT)2 receptors can be partially characterized by their sensitivity to ketanserin blockade and increase in phosphoinositide turnover upon stimulation. Previously, the contraction of guinea pig trachea to 5-HT was shown to be antagonized by the 5-HT2 receptor antagonists ketanserin and LY53857. However, 5-HT did not dramatically increase phosphoinositide turnover in guinea pig trachea, suggesting that the contractile receptor may be different from the classically defined 5-HT2 receptor. The present in vitro studies better characterize this receptor, using diverse serotonergic agonists and antagonists to profile in more detail the contractile serotonergic receptor in guinea pig trachea. With regard to agonists, the 5-HT2 receptor agonists DOI and alpha-methyl-5-HT contracted guinea pig trachea with greater potency than quipazine, 5-methoxytryptamine, 5-carboxamidotryptamine, 8-hydroxy-2-(di-N-propylamino)tetralin and 2-methyl-5-HT. Sumatriptan and 1-(3-chlorophenyl)-piperazine (10 nM-100 microM) were inactive as agonists. A strong correlation between agonist potency (EC50) and reported 5-HT receptor binding affinities was found for both the 5-HT1C (r = 0.890) and 5-HT2 (r = 0.831) receptor. Ketanserin, spiperone, ritanserin, LY53857, 1-napthylpiperazine, 1-(3-chlorophenyl)-piperazine, rauwolscine, ICS 205-930, cyanopindolol and sumatriptan all blocked 5-HT-induced contractions in guinea pig trachea. As occurred with agonist potencies, strong correlations were found between reported 5-HT1C (r = 0.814) and 5-HT2 (r = 0.912) receptor binding affinities in brain membranes and apparent dissociation constants (KB) for the 10 antagonists of 5-HT induced contraction in guinea pig trachea.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunoglobulin G- and immunoglobulin E-mediated airway smooth muscle contraction in the guinea pig

Guinea-pig antibody to ovalbumin was separated into two pools using Protein A Sepharose. The antibody pool retained by the Protein A Sepharose [immunoglobulin (Ig) G pool] was heat stable and persisted in skin sites of the guinea pig less than 7 days. The antibody pool which did not bind to Protein A Sepharose (IgE pool) was heat labile and persisted in guinea-pig skin at least 10 days. Both antibody pools were capable of mediating contraction of isolated guinea-pig tracheal and lung parenchymal strips using airway strips passively sensitized in vivo or in vitro. Although the majority of the skin sensitizing ability of the IgE pool was destroyed by heating at 56 degrees C for 4 hr, its ability to mediate airway contraction was only partially inhibited. Experiments examining [125I]Protein A binding of the antibody pools indicated that the contractions seen in airways sensitized with IgE pool was not due to contamination with IgG. These studies provide a system for examining antagonism of and mediators responsible for IgG-vs. IgE-mediated airway contraction and for evaluating the apparently heat stable properties of IgE.     

Epithelial factors: modulation of the airway smooth muscle tone

Summary— The airway epithelium is composed of a heterogeneous population of cells. This epithelial layer is not only a physical barrier but also a target responding to a variety of inflammatory mediators. These cells can respond by releasing contracting and relaxing factors to modulate airway responsiveness. They can also metabolize some of the inflammatory mediators. Epithelial damage is a consistent feature of some respiratory conditions, but whether or not such damage contributes to airway disease is for the moment unknown. This review summarizes the literature on the known and proposed roles of the epithelium in the modulation of the airway smooth muscle tone.     

Influence of epithelium on guinea pig airway responses to tachykinins: role of endopeptidase and cyclooxygenase

We have studied the effect of epithelium removal on the contractile responses to exogenous tachykinins and to endogenous tachykinins released by capsaicin in guinea pig trachea. We also studied the effects of inhibition of endopeptidase (by phosphoramidon, 10 microM, and thiorphan, 100 microM), and of inhibition of cyclooxygenase (by indomethacin, 5 microM) on these responses. The order of potency of exogenous tachykinins was neurokinin A (NKA) greater than neurokinin B (NKB) greater than substance P (SP). Epithelium removal enhanced the sensitivity and magnitude of the contractile response to SP, and to a lesser extent NKA and NKB. Capsaicin induced only a weak contractile response in guinea pig trachea. Phosphoramidon and thiorphan increased the sensitivity to SP, but had no effect on acetylcholine responses. The leftwardshift due to epithelium removal was reduced, but not abolished, by phosphoramidon and thiorphan. NKA- and NKB-induced contractions were also enhanced significantly by phosphoramidon. The effect of epithelium removal was abolished for NKA, but not for NKB. Phosphoramidon also increased significantly the contraction to capsaicin in the presence of epithelium, without altering the response obtained in the absence of epithelium. Indomethacin potentiated the sensitivity and maximal contractile response to all the tachykinins with the greatest effect on SP responses, and to capsaicin. The combination of indomethacin with phosphoramidon or thiorphan abolished the effect of epithelium removal for all the tachykinins. We conclude that the effects of exogenous and endogenous tachykinins are enhanced by removal of epithelium and by inhibition of metalloendopeptidase and cyclooxygenase, suggesting that tachykinins may be degraded by epithelial enzymes, and may release relaxant prostanoids in airways.(ABSTRACT TRUNCATED AT 250 WORDS)     

Myosin phosphorylation-independent contraction induced by phorbol ester in vascular smooth muscle.

In isolated rat aorta, carotid artery, tail artery, rabbit aorta and mesenteric artery, but not in ear artery, 1 microM 12-deoxyphorbol 13-isobutyrate (DPB) induced a sustained contraction. However, DPB increased cytosolic Ca++ concentration ([Ca++]i) only in rat aorta and carotid artery. Similar results were obtained with phorbol 12,13-dibutyrate, although the inactive phorbol ester, 4-alpha-phorbol 12,13-dibutyrate, was ineffective. In rat aorta, DPB-induced contraction was followed by an increase in 20 kDa myosin light chain (MLC) phosphorylation. Both contraction and MLC phosphorylation stimulated by DPB were greater than those due to high K+ for a given increase in [Ca++]i. A Ca++ channel blocker, verapamil, decreased the DPB-induced increments in [Ca++]i and MLC phosphorylation to their respective resting levels, although contraction was inhibited only slightly. In the absence of external Ca++ (with 0.5 mM ethyleneglycol bis(beta-aminoethyl-ether)tetraacetic acid), DPB induced sustained contraction without increasing [Ca++]i or MLC phosphorylation. This contraction was followed by an increase in stiffness and force recovery after a shortening step. These results suggest that the contraction induced by DPB in rat aorta is due to increase in [Ca++]i followed by MLC phosphorylation and Ca++ sensitization of MLC phosphorylation. In the presence of verapamil or in the absence of external Ca++, DPB may increase cross-bridge cycling by activating an unknown mechanism that is not dependent on an increase in MLC phosphorylation.     

Stimulation of the Na(+)-K(+) pump in cultured guinea pig airway smooth muscle cells by serotonin

The effect of 5-hydroxytryptamine (5-HT) or serotonin on Na(+)-K(+) pump activity of airway smooth muscle was investigated by measuring (86)Rb(+) uptake in cultured guinea pig tracheal smooth muscle cells. (86)Rb(+) uptake consisted of three distinct components, one sensitive to ouabain, one to bumetanide, and one insensitive to either inhibitor. 5-HT induced a concentration-dependent increase in ouabain-sensitive (86)Rb(+) uptake (EC(50) = 21 nM) but had no effect on bumetanide-sensitive uptake, suggesting that it stimulates the Na(+)-K(+) pump but not the Na(+)-K(+)-Cl(-) cotransporter. Ouabain-sensitive uptake also was stimulated by the 5-HT(2A/2C) agonists 2,5-dimethoxy-4-iodoamphetamine and alpha-methyl-5-HT, but not by the 5-HT(1) agonist 5-carboxamidotryptamine, the 5-HT(1A/1B/2C) agonist 1-(3-chlorophenyl)piperazine, or the 5-HT(3) agonist 1-(3-chlorophenyl)biguanide. 5-HT-stimulated (86)Rb(+) uptake was inhibited by the 5-HT(2A) antagonists ketanserin and spiperone, but not by the 5-HT(1A) antagonist NAN 190 or the 5-HT(3) antagonist Y25310. 5-HT-stimulated (86)Rb(+) uptake was inhibited by reducing extracellular Na(+) concentration and by the Na(+)-H(+) exchange inhibitors dimethylamiloride and 5-(N-methyl-N-isobutyl)-amiloride. These observations suggest that 5-HT stimulates the Na(+)-K(+) pump of airway smooth muscle via 5-HT(2A) receptors by a mechanism dependent on Na(+) influx, possibly through the Na(+)-H(+) exchanger. Because stimulation of the Na(+)-K(+) pump produces hyperpolarization, this may represent a negative-feedback mechanism that opposes contraction in response to 5-HT.     

Histamine N-methyltransferase controls the contractile response of guinea pig trachea to histamine.

The contractile response of isolated guinea pig trachea to histamine was potentiated in the presence of the histamine N-methyltransferase (HMT) inhibitor SKF 91488, whereas the diamine oxidase inhibitor aminoguanidine was without effect. SKF 91488 shifted in a concentration-dependent fashion the concentration-response curves to histamine to lower concentrations with the maximum by 1 log unit. The trachea contained significant HMT activity (45.4 +/- 5.0 pmol/min/mg protein). In situ hybridization to detect HMT mRNA indicated that HMT mRNA was present in the epithelium and endothelium, being more abundant in the former. Removal of the epithelium shifted the concentration-response curves to histamine to lower concentrations by 0.8 log unit, and SKF 91488 caused only a slight shift of histamine concentration-response curves in tissues denuded of epithelium. These findings suggest that HMT regulates the contractile response of guinea pig trachea to histamine, and epithelial removal-induced bronchial hyperresponsiveness to histamine is largely explained by the loss of HMT in the epithelium.     

Lack of local neurogenic involvement in the hyperreactivity induced by epithelium removal in guinea pig trachea

Airway epithelium removal produces tracheobronchial smooth muscle hyperreactivity to different constrictor agonists. Aside from the loss of an epithelium-derived relaxant factor, other mechanisms such as production of local axon reflex could hypothetically be involved. In the present work we investigated the effect of nerve activity inhibition or ganglionic transmission blockade in the epithelium removal-induced hyperreactivity in guinea pig trachea. Tetrodotoxin, tetracaine or hexamethonium did not modify the enhanced sensitivity of denuded tracheas to histamine, suggesting that, at least under these experimental conditions, local axon or ganglionic reflexes are not involved.     

Role of airway epithelium on the reactivity of smooth muscle from guinea pigs sensitized to ovalbumin by inhalatory method

It has been demonstrated that the lack of epithelium in healthy airways from different species modifies the reactivity of tracheobronchial smooth muscle. In the present work we have investigated the effect of airway epithelium removal in tracheal chains from guinea pigs sensitized to ovalbumin by inhalatory route and unsensitized animals. We found that in both groups the mechanical removal of airway epithelium produced an increase in the tracheal sensitivity and maximum contractile response to histamine. The greatest responses were observed in epithelium-lacking sensitized tracheas. These findings, at least in vitro, support the idea that the damage of respiratory epithelium plays an important role in modulating the airway reactivity and this is more noteworthy in tracheal chains from previously sensitized guinea pigs.     

Influence of cartilage on reactivity and on the effectiveness of verapamil in guinea pig isolated airway smooth muscle

The authors have examined the effects of cartilage removal on smooth muscle reactivity and the action of verapamil in guinea pig trachealis. In preparations devoid of cartilage, smooth muscle reactivity to both histamine and KCl was reduced. Reactivity to methacholine was unaffected by cartilage removal. In the absence of cartilage, verapamil had a greater depressant effect on the maximum responses to histamine and methacholine than in intact tissues. Similarly, verapamil was more potent against histamine- and methacholine-induced responses in the absence of cartilage where a greater shift to the right was seen in the concentration-response curves when compared with cartilage-containing controls. The spasmolytic action of verapamil on methacholine-induced responses was greater in the absence of cartilage and was greater than its antispasmogenic activity against methacholine (whether or not cartilage was present). Thus, cartilage removal reduces muscle reactivity and increases the potency of verapamil in guinea pig trachealis.     

An examination of the influence of the epithelium on contractile responses to peptidoleukotrienes and blockade by ICI 204,219 in isolated guinea pig trachea and human intralobar airways

The influence of the epithelium on antagonism by ICI 204,219 of contractile responses to peptide leukotriene (LT) agonists was examined in guinea pig tracheal and human bronchial rings. The -log molar KB values for ICI 204,219 were found to be independent of the epithelium in both tissues. Even though uninfluenced by the epithelium, the -log molar KB values for ICI 204,219 were about 10-fold smaller in human airways than in guinea pig trachea. Removal of the epithelium from guinea pig trachea resulted in small leftward shifts of the concentration-response curves to LTC4 and LTD4 and rightward shifts of the concentration-response curves to LTE4 when examined in the presence of indomethacin. The potentiation of LTC4 and LTD4 by epithelium removal was not seen in the presence of inhibitors of the transformation of LTC4 to LTD4 and LTD4 to LTE4. The influence of the epithelium on responses to LTE4 remained in the presence of these metabolic inhibitors. The lipoxygenase inhibitors nordihydroguaiaretic acid, B755C, Rev 5901 and AA861 antagonized responses to LTE4 in the presence, but not in the absence of epithelium. In human airways, epithelium removal resulted in a small leftward shift of the concentration-response curve to LTD4 whereas responses to LTC4 and LTE4 were unaltered. This effect was not observed in the presence of indomethacin, relating it to reduced release of cyclooxygenase products. These data suggest that contractile responses of guinea pig trachea to LTE4 are modulated by LTE4-induced release of 5-lipoxygenase product(s) only when the epithelium is present.(ABSTRACT TRUNCATED AT 250 WORDS)     

Insulin inhibits the increased contractile force induced by epinephrine in isolated guinea pig heart muscle

While the mechanism of positive inotropic action of insulin is not yet fully known, glycose, insulin and potassium solution (GIK solution) has been used in cardiopulmonary resuscitation. Catecholamines continue to be the first line drug to increase blood pressure during cardiac arrest. This study was designed to determine the interaction of insulin and epinephrine on guinea pig papillary heart muscle. The mechanical response of papillary muscle isolated from guinea pig ventricle was observed. Epinephrine increased the twitch tension with a mean maximum contractile force of 766.4% of control. Insulin decreased the increased tension induced by epinephrine to 103.8% of control. This blocking phenomena was not influenced by preadministered insulin. Likewise, the effect of epinephrine was not affected by preadministered insulin.     

Comparative distribution of smooth muscle postsynaptic contractile responses in canine trachea and bronchus in vivo

The response of canine tracheal and bronchial smooth muscle to i.a. administered agonists causing smooth muscle contraction was compared in 22 mongrel dogs in vivo. Tracheal and bronchial contractile responses were measured isometrically in situ in the same dogs. In nine dogs, dose-response curves were generated with i.a. acetylcholine and histamine (10(-10) to 10(-6) mol) in a 4-cm tracheal segment and a 1-cm segment of third order bronchus. The tracheal response to i.a. histamine was 36.5 +/- 4.48% of the response to equivalent doses of acetylcholine. In bronchus, the contraction caused by histamine was 81.0 +/- 2.83% of the cholinergic contractile response (P less than .001). In five dogs having beta adrenergic blockade with propranolol, tracheal contraction to 10(-8) to 10(-6) mol i.a. norepinephrine was 27.3 +/- 4.2% of the response to acetylcholine. However, in bronchus, contraction to norepinephrine was 218 +/- 16.6% of the response to equivalent doses of acetylcholine (P less than .001). Phentolamine (200-400 micrograms/kg i.a.) caused 79 to 100% blockade of the tracheal and bronchial response to i.a. norepinephrine. Cholinergic contraction was blocked specifically with 5 micrograms/kg i.a. of atropine. It is concluded that there is substantial heterogeneity in the contractile responses of canine trachea and bronchus in situ. Relative to cholinergic contraction, both histamine and alpha adrenergic stimulation cause substantially greater contraction of airway smooth muscle in the third order bronchus than in trachea.     

苦豆子对豚鼠内脏平滑肌收缩活动的干预

目的：观察苦豆子水煎剂对豚鼠离体内脏平滑肌作用的影响，分析其发挥作用途径。 方法：实验于2004—12在宁夏医学院基础学院生理实验室完成。①选用健康成年三色毛豚鼠24只，雌雄不拘。②苦豆子（由银川市中医院提供，由该院检定）被制备成1kg／L的水煎剂，实验的系列质量浓度为1&;#215;10^-4，3&;#215;10^-4，1&;#215;10^-3，3&;#215;10^-3，1&;#215;10^-2，2&;#215;10^-2kg／L。③实验方法：实验时分别取出豚鼠胆囊、胃、小肠及膀胱。每个胆囊制备3条平滑肌肌条，共72条；胃、小肠及膀胱各制备12条平滑肌肌条。累积于置胆囊、胃、小肠及膀胱平滑肌肌条各12条的肌槽中加入1&;#215;10^-4，3&;#215;10^-4，1&;#215;10^-3，3&;#215;10^-3，1&;#215;10^-2，2&;#215;10^-2kg／L苦豆子水煎剂，加药间隔2min。容量50μL。④按随机抽签法将其余60条胆囊肌条分为5组：阿托品＋苦豆子组、酚妥拉明＋苦豆子组、维拉帕米＋苦豆子组、苯海拉明＋苦豆予组、吲哚美辛＋苦豆子组，每组12条。上述5组分别加入拮抗剂阿托品（胆碱能M受体阻断剂）1&;#215;10^-6mol／L，酚妥拉明（肾上腺素能α受体阻断剂）1&;#215;10^6mol／L，维拉帕米（Ca^2＋拮抗剂）1&;#215;10^-7mol／L，苯海拉明（组织胺H1受体阻断剂）1&;#215;10^-6mol／L，吲哚美辛（前列腺隶受体阻断剂）1&;#215;10^6mol／L后2min再依次加入前述“累积加药”中各质量浓度苦豆子。⑤通过JH-2肌肉张力换能器将信号输出BL-410生物机能实验系统读出标本的张力、收缩波平均振幅及收缩频率的变化值。⑥数据间差异性比较采用均数t检验。 结果：①累积加入苦豆子水煎剂1&;#215;10^-4，3&;#215;10^-4，1&;#215;10^-3，3&;#215;10^-3，1&;#215;10^-2.2&;#215;10^-2kg／L后，胆囊肌条张力逐渐增高、收缩频率逐渐加快、收缩波平均振幅逐渐减小。（函当苦豆子水煎剂累积质量浓度为2&;#215;10^-2kg／L时，酚妥拉明＋苦豆子组离体胆囊肌条张力和收缩频率明显低于或慢于苦豆子组（t=2，3401，2．1404，P〈0．05），而收缩波平均振幅明显高于苦豆子组（t=2．8256，P〈0．05）。维拉帕米＋苦夏子组离体胆囊肌条张力明显低于苦豆子组（t=2．3464，P〈0．05）。③当苦豆子水煎剂累积质量浓度为1&;#215;10^-2kg／L时，酚妥拉明＋苦夏子组离体胆囊肌条张力明显低于苦豆子组（t=2．430，P〈0．05），而收缩波平均振幅明显高于苦豆子组（t=2．2279，P〈0．05）。维拉帕米＋苦豆子组离体胆囊肌条张力明显低于苦豆子组（t=2．6576，P〈0．05）。④累积加入不同质量浓度苦赢子水煎剂后对豚鼠胃、小肠及膀胱肌条的张力、收缩波平均振幅及收缩频率无明显影响（P〉0．05）。 结论：①苦豆子水煎刺可呈剂量依赖性增高胆囊平滑肌肌条的张力、加快收缩频率、减小收缩波平均振幅，其作用可被酚妥拉明及维拉帕米部分阻断，且该种作用可能与胆囊平滑肌细胞膜上的肾上腺素能Ⅱ受体和细胞膜上的Ca^2＋通道有关。②苦豆子水煎剂对豚鼠胃、小肠及膀胱平滑肌的收缩活动无明显影响。     

苦豆子对豚鼠内脏平滑肌收缩活动的干预

目的:观察苦豆子水煎剂对豚鼠离体内脏平滑肌作用的影响,分析其发挥作用途径。方法:实验于2004-12在宁夏医学院基础学院生理实验室完成。①选用健康成年三色毛豚鼠24只,雌雄不拘。②苦豆子(由银川市中医院提供,由该院检定)被制备成1kg/L的水煎剂,实验的系列质量浓度为1×10-4,3×10-4,1×10-3,3×10-3,1×10-2,2×10-2kg/L。③实验方法:实验时分别取出豚鼠胆囊、胃、小肠及膀胱。每个胆囊制备3条平滑肌肌条,共72条;胃、小肠及膀胱各制备12条平滑肌肌条。累积于置胆囊、胃、小肠及膀胱平滑肌肌条各12条的肌槽中加入1×10-4,3×10-4,1×10-3,3×10-3,1×10-2,2×10-2kg/L苦豆子水煎剂,加药间隔2min,容量50μL。④按随机抽签法将其余60条胆囊肌条分为5组:阿托品 苦豆子组、酚妥拉明 苦豆子组、维拉帕米 苦豆子组、苯海拉明 苦豆子组、吲哚美辛 苦豆子组,每组12条。上述5组分别加入拮抗剂阿托品(胆碱能M受体阻断剂)1×10-6mol/L,酚妥拉明(肾上腺素能α受体阻断剂)1×10-6mol/L,维拉帕米(Ca2 拮抗剂)1×10-7mol/L,苯海拉明(组织胺H1受体阻断剂)1×10-6mol/L,吲哚美辛(前列腺素受体阻断剂)1×10-6mol/L后2min再依次加入前述“累积加药”中各质量浓度苦豆子。⑤通过JH-2肌肉张力换能器将信号输出BL-410生物机能实验系统读出标本的张力、收缩波平均振幅及收缩频率的变化值。⑥数据间差异性比较采用均数t检验。结果:①累积加入苦豆子水煎剂1×10-4,3×10-4,1×10-3,3×10-3,1×10-2,2×10-2kg/L后,胆囊肌条张力逐渐增高、收缩频率逐渐加快、收缩波平均振幅逐渐减小。②当苦豆子水煎剂累积质量浓度为2×10-2kg/L时,酚妥拉明 苦豆子组离体胆囊肌条张力和收缩频率明显低于或慢于苦豆子组(t=2.3401,2.1404,P<0.05),而收缩波平均振幅明显高于苦豆子组(t=2.8256,P<0.05)。维拉帕米 苦豆子组离体胆囊肌条张力明显低于苦豆子组(t=2.3464,P<0.05)。③当苦豆子水煎剂累积质量浓度为1×10-2kg/L时,酚妥拉明 苦豆子组离体胆囊肌条张力明显低于苦豆子组(t=2.430,P<0.05),而收缩波平均振幅明显高于苦豆子组(t=2.2279,P<0.05)。维拉帕米 苦豆子组离体胆囊肌条张力明显低于苦豆子组(t=2.6576,P<0.05)。④累积加入不同质量浓度苦豆子水煎剂后对豚鼠胃、小肠及膀胱肌条的张力、收缩波平均振幅及收缩频率无明显影响(P>0.05)。结论:①苦豆子水煎剂可呈剂量依赖性增高胆囊平滑肌肌条的张力、加快收缩频率、减小收缩波平均振幅,其作用可被酚妥拉明及维拉帕米部分阻断,且该种作用可能与胆囊平滑肌细胞膜上的肾上腺素能α受体和细胞膜上的Ca2 通道有关。②苦豆子水煎剂对豚鼠胃、小肠及膀胱平滑肌的收缩活动无明显影响。     

Effects of milrinone on contractile responses of guinea pig trachea, lung parenchyma and pulmonary artery

The effects of milrinone, a bipyridine with known vasodilator activity, on guinea pig tracheal-spirals, lung parenchymal strips and pulmonary artery rings in vitro were compared with the effects of isoproterenol and aminophylline on these tissues. The concentration of milrinone that produced 50% relaxation (IC50) of tracheal spirals constricted by carbachol was 3.6 X 10(-5) M. Isoproterenol (IC50, 9.5 X 10(-8) M) was significantly (P less than .001) more potent and aminophylline (IC50, 1.2 X 10(-4) M) was significantly (P less than .001) less potent than milrinone in this effect. The IC50 for milrinone for lung parenchymal strips contracted by histamine was 3.2 X 10(-5) M, whereas the IC50 for isoproterenol was significantly (P less than .001) less, 1.4 X 10(-7) M; aminophylline produced only limited relaxation of lung parenchymal strips. Milrinone relaxed pulmonary artery rings constricted by norepinephrine with an IC50 of 3.8 X 10(-6) M, whereas neither isoproterenol nor aminophylline produced a 50% relaxation. Pretreatment of tracheal spirals, lung parenchymal strips and pulmonary artery rings with 1.6 X 10(-4) M milrinone inhibited subsequent contraction by carbachol, histamine and norepinephrine, respectively. The relaxant effects of milrinone were not influenced by treatment with atropine, cimetidine, mepyramine, phentolamine or propranolol. However, indomethacin blocked milrinone's relaxant effects on tracheal spirals effectively, but not on pulmonary artery rings or lung parenchymal strips, suggesting distinct modes of action on various tissue types.