Biomedical subjects

J F Souhrada

Publications and source records attributed to J F Souhrada.

At least 19 recordsLinked to original sources

PubMed1999

Effect of ipratropium bromide treatment on oxygen saturation and sleep quality in COPD.

STUDY OBJECTIVES: Patients with COPD are at risk of experiencing a deterioration in arterial oxygen saturation (SaO2) during sleep, which is generally most pronounced during rapid eye movement (REM) sleep. Increased cholinergic tone has been suggested as a contributing factor to this decrease in SaO2. Therefore, we investigated whether 4-week treatment with ipratropium bromide inhalation solution 0.02% (qid) could improve sleep characteristics in COPD. DESIGN: Randomized, placebo-controlled, double-blind, two-arm parallel study of 4 weeks of treatment with ipratropium bromide solution or placebo. SETTING: Multicenter investigation. PATIENTS: Thirty-six patients with moderate-to-severe COPD (FEV1 < 65% of predicted). MEASUREMENTS AND RESULTS: Evaluation included polysomnographic, pulmonary function, and subjective quality of sleep (visual analog scale [VAS]) assessments. It was found that 4 week of treatment with ipratropium bromide solution in patients with COPD led to the following: (1) a significant (p = 0.05) improvement in mean nocturnal SaO2 with the more severe the nocturnal desaturation, the greater the improvement in SaO2; (2) significant (p = 0.03) improvement in perceived sleep quality (VAS: 5.5 +/- 0.5 after placebo; 7.2 +/- 0.5 after ipratropium); (3) a significant (p = 0.05) increase in REM sleep time (48.6 +/- 6.3 min after placebo; 66.5 +/- 6.4 min after ipratropium) with no effect on other sleep stages or total sleep time; and (4) a significant (p = 0.01) increase in pre-sleep FVC and flow rate at 50% of the vital capacity. CONCLUSIONS: These findings demonstrate that ipratropium bromide therapy can improve sleep SaO2 as well as sleep quality in patients with moderate-to-severe COPD.

Adult↗

PubMed1996

Role of phospholipase C and tyrosine kinase systems in growth response of human airway smooth muscle cells.

The primary culture of confluent human airway smooth muscle (ASM) cells were exposed up to 5 days to human recombinant interleukin (IL)-1 beta in the presence of indomethacin and 1% fetal bovine serum. The proliferation was assessed by a [3H]thymidine incorporation and direct cell count. We found that IL-1 beta significantly increased thymidine incorporation into and cell count of ASM cells in a concentration-dependent manner. Pretreatment of cells with specific polyclonal antibodies against platelet-derived growth factor (PDGF-BB homodimer) completely inhibited the IL-1 beta-induced increase in thymidine incorporation. The PDGF-BB, at the concentrations of 1.5 and 2.5 ng/ml, stimulated the proliferation of ASM cells. The proliferation action of IL-1 beta was potentiated when PDGF-BB was added into the medium in combination with IL-1 beta. Pretreatment of cells with genistein (0.37 microM), a specific tyrosine kinase inhibitor, attenuated the proliferative effect of IL-1 beta and PDGF-BB. To clarify whether these growth stimuli (IL-1 beta and PDGF-BB) activated phospholipase C (PLC), we examined the formation of phosphatidylinositols. We observed that both agents significantly increased phosphoinositide turnover. In contrast, genistein pretreatment (0.37 microM) prevented formation of inositol 1,4,5-trisphosphate (IP3), as induced by IL-1 beta and/or PDGF-BB. This study demonstrates that both IL-1 beta and PDGF-BB could induce proliferation of ASM cells through the activation of tyrosine kinase and PLC, which in turn stimulate the formation of IP3, a second messenger molecule.

Becaplermin↗

PubMed1995

IL-1 beta and IL-6 induce hyperplasia and hypertrophy of cultured guinea pig airway smooth muscle cells.

Guinea pig airway smooth muscle (ASM) cells were maintained in a primary tissue culture (passages 1-3). Cells were exposed to human recombinant interleukin-1 beta (IL-1 beta; 20-100 pg/ml) or interleukin-6 (IL-6; 1-4 ng/ml) in the presence of indomethacin (1 microgram/ml) for up to 5 days. Proliferation of ASM cells was assessed with two techniques, direct counting of cells with a hemacytometer and [3H]thymidine incorporation corrected for total protein content. Hypertrophy of ASM cells was assessed by [3H]leucine incorporation (evaluation of protein synthesis), determination of total DNA content, DNA content per cell, and protein content per cell. We observed that the exposure of ASM cells to human recombinant IL-1 beta or IL-6, in all studied concentrations, significantly increased the number of cells as well as [3H]thymidine incorporation into ASM cells. We also found that exposure of ASM to these two cytokines increased [3H]leucine incorporation into the ASM cells and increased protein content and DNA content per single cell. These changes were also concentration dependent. We conclude that the two proinflammatory cytokines, IL-1 beta and IL-6, which are present in asthmatic lungs, increased the proliferation of ASM cells (hyperplasia) as well as their overall size and size of their nuclei, as measured by biochemical markers. These findings are compatible with the presence of ASM hypertrophy.

Animals↗

PubMed1993

Effect of IgG1 and its fragments on resting membrane potential of isolated tracheal myocytes.

We enzymatically isolated airway smooth muscle cells from the trachea of guinea pigs (400-600 g body wt). After removal of connective tissue, strips of trachealis muscle were cleaned under a dissecting microscope and incubated with collagenase (type I, 1 mg/ml) and elastase (type I, 15 U/ml) for 20 min. Cells were resuspended in Dulbecco's modified Eagle's medium and seeded on 1.5% gelatin-coated Petri dishes (35 mm). The viability of cells was assessed by trypan blue exclusion. Individual myocytes were impaled with glass microelectrodes (input resistance 90-100 M omega). Resting membrane potential (Em) was determined before and after administration of 1) immune serum, 2) highly purified specific immunoglobulin G1 (IgG1), and 3) enzymatically prepared fragments of IgG1-F(ab')2 and Fc. We found that 1) Em of isolated tracheal myocytes is -60.5 +/- 0.5 mV; 2) some myocytes exhibit spontaneous electrical rhythm with mean frequency of 16.9 +/- 12 min-1 and mean amplitude of 3.7 +/- 0.6 mV; 3) immune serum, IgG1, and Fc fragments induced a biphasic change in Em: the initial mean depolarization (-51.5 +/- 0.8 mV) was followed by a steady-state hyperpolarization (-68.3 +/- 0.6 mV); and 4) pretreatment of myocytes with amiloride (10(-5) M) or exposure of myocytes to a low-sodium environment prevented changes in Em induced by the passive in vitro sensitization. It is likely that airway smooth muscle cells have a low-affinity Fc receptor, the occupancy of which leads to activation of amiloride-sensitive sodium influx.

Amiloride↗

PubMed1993

Inhibitory effect of staurosporine on protein kinase C stimulation of airway smooth muscle cells.

Phospholipid/calcium-dependent protein kinase (protein kinase C [PKC]) is a critical system in signal transduction of many different cells including airway smooth muscle (ASM) cells. We have previously shown that after administration of different phorbol esters, specific activators of PKC, characteristic electrical and contractile changes of ASM cells can be demonstrated. Similarly, our data showed that stimulation of PKC is implicated in the process of sensitization and the specific antigen challenge response of ASM cells. In this study we examined the effect of staurosporine, a microbial alkaloid, which has been reported to be a specific inhibitor of PKC, on sensitization- and specific antigen challenge-induced electrical and contractile changes of ASM cells. The effect of staurosporine was compared with those of amiloride, furosemide, and compounds NA-0345 and H-7, both synthetic PKC inhibitors. We used ASM preparations isolated from adult male guinea pigs (Camm-Hartley strain). Changes in both membrane potential (Em), measured by a glass microelectrode technique, and isometric force, measured by copper-beryllium strain gauge, were continuously monitored. Experiments were conducted with optimal length (Lmax) of ASM preparations and at 37 degrees C. We found that the exposure of ASM preparations to staurosporine, NA-0345, H-7, amiloride, and furosemide (all in 10(-12) to 10(-4) M) had no measurable effect on the resting membrane potential or isometric force of ASM preparations. In contrast, pretreatment of ASM preparations with staurosporine, NA-0345, H-7, amiloride, or furosemide significantly attenuated (p < 0.001) phorbol myristate acetate-induced changes of ASM preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1993

Interleukin-1 beta stimulates the proliferation of cultured airway smooth muscle cells via platelet-derived growth factor.

Bronchoalveolar lavage fluid from symptomatic asthmatics contains elevated levels of several proinflammatory interleukins including interleukin-1 beta (IL-1 beta). Biologic activities of IL-1 beta are considered to be critical in the inflammatory process. Since these characteristics include mitogenic properties, we investigated the effect of IL-1 beta on the proliferation of airway smooth muscle (ASM) cells isolated from guinea pig tracheas. Primary tissue culture of ASM cells was maintained in media containing 0%, 1%, or 10% fetal bovine serum (FBS). Cultures were exposed up to 6 days to human recombinant IL-1 beta (20, 40, or 100 pg/ml) in the presence or absence of indomethacin. The proliferation of ASM cells was assessed with two techniques: a direct counting of cells with a hemocytometer and/or with a [3H]-thymidine incorporation, an established marker of DNA synthesis. The evaluation was done daily, up to the sixth day after exposure of cells to different doses of IL-1 beta. We found that the exposure of ASM cells to human recombinant IL-1 beta significantly (P < 0.01) increased the number of tracheal myocytes as well as the [3H]-thymidine incorporation into ASM cells. These changes were dependent upon the dose of IL-1 beta and the concentration of FBS in the cultured medium. The most active proliferation of ASM cells was observed in medium containing 1% FBS, indomethacin (1 microgram/ml), and IL-1 beta (100 pg/ml). The presence of indomethacin in the culture medium was essential to demonstrate the proliferative effect of IL-1 beta.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Respiratory epithelium-dependent inhibition of protein kinase C of airway smooth muscle cells.

We have examined the effect of phorbol myristate acetate (PMA) on airway smooth muscle (ASM) in the presence and absence of respiratory epithelium (RE) and analyzed the dependence of this response on extracellular sodium, Na+/H+ exchange, calcium, and cyclooxygenase products; we determined both the resting membrane potential and isometric force developed by ASM preparations. Removal of RE had no effect on the values of the resting membrane potential of ASM cells. In the presence of RE in the preparation, both electrical and contractile responses to PMA (10(-5) M) were significantly different compared with the response of ASM to PMA without RE. When the RE was present, stimulation of protein kinase C caused only a biphasic response in both membrane potential and isometric force. In either the presence or absence of RE, amiloride (10(-5) M) and a low-sodium solution inhibited both electrical and contractile changes of ASM cells caused by PMA. In the presence or absence of RE, verapamil (10(-5) M) attenuated (P less than 0.05) both electrical and contractile responses of ASM cells as induced by PMA. Verapamil, however, had no effect on the last phase of PMA-induced response. Pretreatment of preparations with indomethacin (10(-6) M) changed the PMA-induced response of ASM with RE to a response usually observed in ASM without RE. Finally, the incubation of tracheal preparations without RE with prostaglandin E2 (10(-8) M) altered the response of these preparations in such a way that their electrical and contractile response to PMA was essentially identical to the PMA response observed in preparations with an intact RE.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Sodium and calcium influx induced by phorbol esters in airway smooth muscle cells.

The second messenger protein kinase C (PKC) may play a critical role in the regulation of smooth muscle tone. In this study we examined how a direct stimulation of PKC in airway smooth muscle (ASM) cells influences the electrical and contractile properties of these cells. ASM preparations were obtained from adult male guinea pigs (Camm-Hartley strain). Changes in both the resting membrane potential (Em), as measured by a glass microelectrode technique, and the isometric force, measured by a copper-beryllium strain gauge, were continuously monitored. All experiments were done at the optimal length (Lmax) of ASM preparations and a temperature of 37.0 +/- 0.5 degrees C. The effects of phorbol myristate acetate (PMA), phorbol 12,13-diacetate (PDA), and 12,deoxyphorbol-13-isobutyrate (DPB) were investigated (with concentrations ranging from 10(-10) to 10(-4) M). We found that: (1) administration of all three phorbol esters caused a triphasic electrical and contractile response of ASM preparations showing initial, rapid depolarization, an increase in the isometric force, and slow hyperpolarization and relaxation of ASM followed by slow depolarization and an increase in the isometric force; (2) the presence of specific PKC inhibitor H-7 (10(-5) M) prevented development of both electrical and contractile events as induced by tested phorbols; (3) amiloride (10(-5) M) attenuated first- and second-phase responses, whereas furosemide (10(-5) M) inhibited all three responses (a sodium-free environment attenuated all three responses); (4) ouabain (10(-5) M) inhibited a second-phase response, whereas verapamil (10(-6) M) partially attenuated all three phases.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

The role of protein kinase-C in sensitization and antigen response of airway smooth muscle.

Recently, we reported the characteristic electrical and contractile changes of airway smooth muscle (ASM) preparations after administration of highly purified antiovalbumin immunoglobin G1 (IgG1). Because these changes are comparable to those we observed after administration of several phorbol esters, we theorized that sensitization of ASM with IgG1 leads to the activation of protein kinase-C. Therefore, in this study we examined the effect of two inhibitors of protein kinase-C on the sensitization-induced changes of ASM cells. ASM preparations were obtained from adult male guinea pigs (Camm-Hartley strain). Changes in both the resting membrane potential, as measured by a glass microelectrode technique, and changes in the isometric force, measured by a copper-beryllium strain gauge, were continuously monitored. Experiments were conducted at the optimal length of ASM preparations and a temperature of 37 degrees C. The preparations were pretreated with H-7 (1-(5-isoquinoilinyl-sulfonyl)-2-methyl piperazine) or NA-0345 (N,N-dimethylamino-methyl-SF2370) both protein kinase-C inhibitors, passively sensitized with IgG1 and consequently exposed to a specific antigen. We found that pretreatment inhibited the initial depolarization and the increase in the isometric force, usually observed after administration of IgG1, and that it attenuated ovalbumin-induced depolarization and sustained increase in the isometric force. These effects were concentration-dependent and were observed only when protein kinase-C inhibitors preceded administration of IgG1. Finally, H-7 pretreatment had no effect on KCl- or substance-P-induced physiologic changes but partially attenuated response to histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1988

Doxazosin in patients with hypertension.

The antihypertensive effects and steady-state pharmacokinetics of doxazosin, as well as the bioequivalence of four dosage forms, were studied in 25 hypertensive patients. For an 8 mg daily dose mean Cmax at steady-state for all patients was 108 ng/ml; the mean tmax was 1.8 h. The mean terminal elimination half-life was 22 h. The four tablets containing 1, 2, 4, or 8 mg of doxazosin were bioequivalent in delivering the 8 mg dose. In patients with mild to moderate hypertension, 26-day treatment with doxazosin resulted in blood pressure reduction of 10/7 mmHg in the supine and 13/18 mmHg in the standing position. Adverse effects were generally mild and of brief duration.

Adult↗

PubMed1988

Corticosteroids attenuate sensitization-induced membrane changes in airway smooth muscle cells.

Serum from immunized guinea pigs or highly purified IgG1 induces specific changes in electrical and contractile characteristics of airway smooth muscle (ASM) cells. In this study, the effect of hydrocortisone and prednisolone pre-treatment on the events caused by a passive in vitro sensitization of ASM cells was investigated. ASM preparations isolated from male guinea pigs were exposed to immunized serum (1:10 dilution) together with different concentrations of hydrocortisone or prednisolone administered simultaneously or 30, 120 or 240 min before addition of immunized serum. During sensitization as well as during consecutive specific antigen challenges (1 mg/ml ovalbumin), both the resting membrane potential (Em) and isometric force developed by airway smooth muscle preparations were determined. Em was determined with glass microelectrodes and isometric force was simultaneously measured with a copper-berylium strain gauge. Pretreatment with both hydrocortisone and prednisolone (in the range of 10(-8)-10(-4) M) attenuated sensitization-induced transient depolarization and steady state hyperpolarization of ASM cells and decreased the sensitization-induced development of the isometric force. Furthermore, pretreatment with either steroid significantly attenuated electrical and contractile responses to a specific antigen challenge. Inhibition of the events observed during sensitization occurred at steroid concentrations as low as 10(-8) M. We have also found that the duration of exposure of ASM cells to either of the tested steroids is critical in determining the magnitude of this inhibitory effect and seems to be more important than concentration of tested steroids.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Hormones↗

PubMed1988

The inhibition of sodium influx attenuates airway response to a specific antigen challenge.

1. We have previously observed that manipulation of Na+ availability during passive in vitro sensitization altered electrophysiological and contractile changes of airway smooth muscle cells. The purpose of this study was to establish whether interference with Na+ influx during sensitization also influences the response of airway smooth muscle, both in vivo and in vitro, to a specific antigen challenge. 2. Isolated segments of trachea which had been sensitized to ovalbumin in the presence of the Na+ channel-blocking agent amiloride (10(-5) M) showed no electrical or contractile response to ovalbumin in spite of their ability to respond to histamine (10(-5) M). 3. Airway smooth muscle preparations sensitized to ovalbumin in a Na+-deficient medium failed to show any contractile response after exposure to ovalbumin and only a small depolarization of airway smooth muscle cells was detected. 4. Guinea-pigs were passively sensitized in vivo either in the absence of, or following pretreatment with, amiloride (1 mg kg-1 s.c.). These animals were then exposed to an ovalbumin inhalation challenge and both lung resistance (RL) and dynamic lung compliance (Cdyn) were measured. 5. After an inhalation challenge of sensitized animals, we observed a significant increase in lung resistance (RL) achieving a maximum of 489% of the baseline values and a decrease in dynamic lung compliance (Cdyn). Twenty min after ovalbumin challenge Cdyn was equivalent to 20% of baseline values. 6. In animals pretreated with amiloride during sensitization, the inhalation challenge caused only a small increase in RL achieving a maximum increase of 148% of baseline values, and a small decrease in Cdyn. Twenty min after ovalbumin challenge Cdy. was equivalent to 98% of baseline values. 7. We concluded that interference with Na' influx during both in vitro and in vivo sensitization attenuates the contractile and electrical responses of airway smooth muscle preparations or the changes in lung resistance and compliance observed after antigen challenge.

Amiloride↗

PubMed1988

Specific reaginic antibody IgG1-induced changes of airway smooth muscle cells.

It was found that 1) an administration of both immunoglobulin G1 (IgG1) or immunized serum caused an immediate depolarization and an increase in the isometric force of airway smooth muscle (ASM) cells, followed by a sustained hyperpolarization and a return of the tone to the base-line values; 2) an IgG1 concentration-dependent relationship was found between a peak depolarization, a peak hyperpolarization, and a peak isometric force; for these events 50% effective dose (ED50) was found to be 0.17, 0.14, and 0.25 microgram/ml of IgG1, respectively; 3) both electrical and contractile responses to ovalbumin of ASM cells sensitized with IgG1 were also dependent on the concentration of IgG1; the ED50 values of this relationship were 0.27 and 0.25 micrograms/ml of IgG1, respectively; 4) amiloride (10(-8) to 10(-5) M) pretreatment and a sodium-deficient environment attenuated sensitized-induced electrical and contractile changes as well as the response of ASM to ovalbumin (0.1%); and 5) pretreatment of ASM with diphenhydramine (10(-5) M) or FPL 55712 (10(-6) M) had no effect on sensitization-induced changes in membrane potential but attenuated electrical and contractile response of ASM to ovalbumin (0.1%).

Amiloride↗

PubMed1987

A transient calcium influx into airway smooth muscle cells induced by immunization.

We have recently reported that sensitization induced biphasic changes of resting membrane potential of the airway smooth muscle cells (Souhrada and Souhrada, 1985). To further clarify whether these changes may have any effect on the airway smooth muscle contractility, we have studied tracheal segments, isolated from Camm-Hartley guinea pigs during passive in vitro sensitization. At that time, airway smooth muscle cells were frequently penetrated with glass microelectrodes and the value of the resting membrane potential was determined simultaneously with changes in the isometric force. It was found that: changes in the resting membrane potential were accompanied by the alteration of the isometric force; during the depolarization phase a transient increase in the isometric force was observed achieving the maximal peak equal to 800 +/- 50 mg; both electrical and contractile changes of airway smooth muscle preparations as induced by sensitization were dependent on the dilution of sensitized serum; ED50 of this relationship was equal to dilution of 1:2500, while the maximal depolarization and the maximal peak isometric force developed at the dilution of serum 1:10; sensitization-induced sodium influx was critical for the development of the isometric force and depolarization, since pretreatment of tissues with amiloride (10(-5) M) or tetrodotoxin (10(-7) M) attenuated these changes; an increase in the isometric force was related to both the opening of the voltage dependent calcium channels and the release of calcium from the intracellular pools.

Airway Resistance↗

PubMed1987

Differential effects of N-formyl-methionyl-leucyl-phenylalanine and substance P on the electrical and contractile properties of airway smooth muscle cells.

We have investigated the effect of substance P (SP) and N-formyl-methionyl-leucyl-phenylanine (f-Met-Leu-Phe) on airway smooth muscle preparations isolated from male guinea pigs. Alterations in both the resting membrane potential and developed isometric force were determined. Addition of SP (10(-10) to 10(-4) M) caused a nonphasic, dose-dependent, sustained depolarization of airway smooth muscle cells, with the concomitant development of increased isometric force. In contrast, f-Met-Leu-Phe (10(-12) to 10(-6) M) induced a biphasic membrane response of airway smooth muscle cells, i.e., a dose-dependent rapid depolarization, followed by prolonged hyperpolarization. During the depolarization phase, a significant transient increase in the isometric force was observed. A selective N-formyl peptide antagonist, t-boc-phenylalanyl-leucyl-phenylalanyl-leucyl-phenylalanine, prevented the f-Met-Leu-Phe-induced changes in membrane polarity and increase in isometric force, as did amiloride (10(-5) M), the selective sodium channel blocker. However, these agents had no effect on SP-induced changes in membrane potential or isometric force. These findings suggest that airway smooth muscle of guinea pigs possess both N-formyl peptide and SP receptors but that occupation of these receptors by their respective agonists leads to functionally distinct responses.

Animals↗

PubMed1985

Sensitization-induced sodium influx in airway smooth muscle cells of guinea pigs.

Airway smooth muscle (ASM) preparations isolated from Camm-Hartley male guinea pigs were passively in vitro sensitized using Austen's technique. During this sensitization, cells were frequently penetrated with glass microelectrodes (a resistance of 80-90 M omega) for a period of 120 min. Simultaneously, changes in the isometric force of ASM preparations were also monitored. It was found that: administration of serum (1:10 dilution) from sensitized animals caused a depolarization of ASM cells (-52.3 +/- 0.7 mV), achieving a peak at 4 min, followed by slow sustained hyperpolarization reaching a steady state after 15 min; (Resulting resting membrane potential of ASM cells was -68.8 +/- 0.5mV as compared to membrane potential of controls equal to -60.0 +/- 0.7 mV); in the presence of ouabain (10(-5)M), the development of hyperpolarization of ASM cells was completely inhibited; replacement of Na+ with choline chloride or lithium chloride partially inhibited the development of depolarization of ASM cells; in the presence of specific sodium entry blocker, amiloride the sensitization-caused depolarization was abolished; the presence of choline chloride, lithium chloride or amiloride in the experimental medium completely inhibited the contractile response of sensitized tissues to a specific antigen; response of ASM preparations to a specific antigen was absent during depolarization of ASM cells, but was always present during their hyperpolarization. It is concluded that in vitro passive sensitization leads to the interaction of serum specific antibodies with the membrane of airway smooth muscle cells so that permeability of membrane for Na+ is increased (transient depolarization) followed by the activation of electrogenic Na+-pump (sustained hyperpolarization). These events seem to determine the contractile response of sensitized ASM cells to a specific antigen.

Amiloride↗

PubMed1985

Role of electrogenic Na+ pump in the response of sensitized airway smooth muscle to antigen.

Airway smooth muscle (ASM) preparations (mid-cervical portion of trachea) were isolated from control Camm-Hartley male guinea pigs and from animals repeatedly sensitized by ovalbumin. Simultaneously with the measurement of isometric force developed by ASM preparations, resting membrane potential (Em) was determined by employing a conventional microelectrode technique. The contractile and electrophysiological responses of normal and sensitized tissues to ovalbumin and histamine (10(-5) M) were measured during inhibition or stimulation of the electrogenic Na+ pump. The activity of the electrogenic Na+ pump was decreased by the temperature of the experimental bath, i.e., 21 +/- 0.5 degrees C, or by ouabain (10(-5) M). We found that: at 37 degrees C Em of ASM in controls was -60.3 +/- 0.4 mV (+/- SE) as compared to -78.2 +/- 0.4 mV (+/- SE) of ASM from resensitized animals (p less than 0.001); cooling (21 degrees C) decreased (p greater than 0.001) Em of ASM of both controls and resensitized animals; warming (40 degrees C) further increased (p less than 0.01) Em of control ASM but had no effect on Em of ASM from resensitized animals; when the electrogenic Na+ pump was inhibited by low temperature (21 degrees C) or by ouabain (10-5 M), ASM preparations from resensitized animals had no measurable response to ovalbumin; in ASM preparations from controls cooling (21 degrees C) potentiated (p less than 0.01) and warming (40 degrees C) attenuated (p less than 0.01) the histamine (10(-5) M) contractile response; in ASM preparations from resensitized animals, when the electrogenic Na+ pump was inhibited, significant (p less than 0.01) contractile and electrical responses to histamine (10(-5) M) were still present.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Immunologically induced alterations of airway smooth muscle cell membrane.

Active and passive sensitization, both in vivo and in vitro, caused significant hyperpolarization of airway smooth muscle cell preparations isolated from guinea pigs. An increase in the contribution of the electrogenic Na+ pump to the resting membrane potential was responsible for this change. Hyperpolarization, as induced by passive sensitization, was not prevented by agents that inhibit specific mediators of anaphylaxis but was abolished when serum from sensitized animals was heated. The heat-sensitive serum factor, presumably reaginic antibodies, appears to be responsible for the membrane hyperpolarization of airway smooth muscle cells after sensitization.

Animals↗