2301
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Varanda W, Finkelstein A. Ion and nonelectrolyte permeability properties of channels formed in planar lipid bilayer membranes by the cytolytic toxin from the sea anemone, Stoichactis helianthus. J Membr Biol 1980; 55:203-11. [PMID: 6106065 DOI: 10.1007/bf01869461] [Citation(s) in RCA: 85] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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2302
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Abstract
The mechanism of in vitro synergistic lysis of sheep erythrocytes by Corynebacterium ovis and Corynebacterium equi was investigated. Hemolysis required (i) the action of phospholipase D from C. ovis, (ii) the action of an extracellular protein of C. equi, and (iii) Mg2+. Maximum lysis required imposition on the system of a fourth condition (step iv), such as chilling. Steps i, ii, and iv occur sequentially and in that order. Mg2+ functions in steps i and ii. The extracellular protein C. equi was purified to homogeneity and found to be a phospholipase C capable of hydrolyzing ceramide phosphate, phosphatidic acid, and all of the isolated major phospholipids of mammalian erythrocyte membranes. The principal features of the synergistic hemolytic system could be reproduced in experiments involving liposomes containing either sphingomyelin or ceramide phosphate and trapped [14C]glucose. We inferred that sphingomyelin of sheep erythrocytes is first converted to ceramide phosphate by C. ovis phospholipase D. On the basis of results with liposomes, we propose that the ceramide phosphate is then converted to ceramide by C. equi phospholipase C. We believe that the resulting in situ ceramide then undergoes dislocation by chilling and perhaps also by virtue of an affinity between ceramide and C. equi phospholipase C. The dislocation of ceramide presumably disorganizes the lipid bilayer sufficiently to result in cell lysis.
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2303
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Abstract
We studied the time course, magnitude and homogeneity of the change in extracellular myocardial potassium activity after acute ligation of the left anterior descending coronary artery in pigs using potassium-sensitive electrodes made from a valinomycin-polyvinyl chloride matrix membrane. We also studied the relationship between the changes in potassium activity and the simultaneous changes in ventricular activation using the reference barrel of the K+ electrode to record ventricular electrograms. We found that the K+ rose sooner, more rapidly and to higher levels than previously reported. The K+ changes occurred in three phases: a phase of rapidly rising K+ that began within seconds of the ligation and lasted 5-15 minutes, a plateau phase that lasted approximately 15 minutes and a phase of slowly rising K+ that extended throughout the longest occlusion (60 minutes) used in this study. The K+ changes were reversed by release of the occlusion during the rapidly rising and plateau phases, but were not reversed by release of the occlusion during the phase of slowly rising K+. Inhomogeneities in the K+ rise appeared between the center and lateral margins of the midmyocardial ischemic zone, between the subendocardium and the subepicardium in the center of the ischemic zone, and between closely spaced electrodes located in the midmyocardial center of the ischemic zone. Thus, the change in K+ activity, as recorded by our electrodes, can be considered an excellent marker of ischemia. Changes in ventricular activation paralleled the K+ rise, the inhomogeneities of K+ rise and the reversal of the K+ rise after release but could not be entirely explained by the change in K+.
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2304
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Alving CR, Iglewski BH, Urban KA, Moss J, Richards RL, Sadoff JC. Binding of diphtheria toxin to phospholipids in liposomes. Proc Natl Acad Sci U S A 1980; 77:1986-90. [PMID: 6929533 PMCID: PMC348635 DOI: 10.1073/pnas.77.4.1986] [Citation(s) in RCA: 41] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Diphtheria toxin bound to the phosphate portion of some, but not all, phospholipids in liposomes. Liposomes consisting of dimyristoyl phosphatidylcholine and cholesterol did not bind toxin. Addition of 20 mol% (compared to dimyristoyl phosphatidylcholine) of dipalmitoyl phosphatidic acid, dicetyl phosphate, phosphatidylinositol phosphate, cardiolipin, or phosphatidylserine in the liposomes resulted in substantial binding of toxin. Inclusion of phosphatidylinositol in dimyristol phosphatidylcholine/cholesterol liposomes did not result in toxin binding. The calcium salt of dipalmitoyl phosphatidic acid was more effective than the sodium salt, and the highest level of binding occurred with liposomes consisting only of dipalmitoyl phosphatidic acid (calcium salt) and cholesterol. Binding of toxin to liposomes was dependent on pH, and the pattern of pH dependence varied with liposomes having different compositions. Incubation of diphtheria toxin with liposomes containing dicetyl phosphate resulted in maximal binding at pH 3.6, whereas binding to liposomes containing phosphatidylinositol phosphate was maximal above pH 7. Toxin did not bind to liposomes containing 20 mol% of a free fatty acid (palmitic acid) or a sulfated lipid (3-sulfogalactosylceramide). Toxin binding to dicetyl phosphate or phosphatidylinositol phosphate was inhibited by UTP, ATP, phosphocholine, or p-nitrophenyl phosphate, but not by uracil. We conclude that (a) diphtheria toxin binds specifically to the phosphate portion of certain phospholipids, (b) binding to phospholipids in liposomes is dependent on pH, but is not due only to electrostatic interaction, and (c) binding may be strongly influenced by the composition of adjacent phospholipids that do not bind toxin. We propose that a minor membrane phospholipid (such as phosphatidylinositol phosphate or phosphatidic acid), or that some other phosphorylated membrane molecule (such as a phosphoprotein) may be important in the initial binding of diphtheria toxin to cells.
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2305
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2306
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Skov PS, Norn S, Schiøtz PO, Permin H, Høiby N. Pseudomonas aeruginosa allergy in cystic fibrosis. Involvement of histamine release in the pathogenesis of lung tissue damage. Allergy 1980; 35:23-9. [PMID: 6154430 DOI: 10.1111/j.1398-9995.1980.tb01713.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Basophil histamine release by P. aeruginosa standard antigen was examined in cystic fibrosis patients chronically infected with mucoid P. aeruginosa (CF +P) and with pronounced antibody response against these bacteria, and in patients without P. aeruginosa infection (CF +P). All the patients showed eosinophil counts and total IgE, which did not differ significantly from that of normal persons. In the absence of patient's sera, histamine release was only found in two patients in the CF +P group, indicating that type I allergy to P. aeruginosa is not predominating in cystic fibrosis. In the presence of patients' sere significantly more of the CF+P patients responded to P. aeruginosa with histamine release compared with the CF-P patients. The response was lost by complement inactivation and regained by reconstitution of the complement activity. The involvement of a type III-mediated complement-dependent histamine release is therefore suggested in the pathogenesis of lung damage in cystic fibrosis.
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2307
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Dunnett J, Nayler WG. Effect of pH on calcium accumulation and release by isolated fragments of cardiac and skeletal muscle sarcoplasmic reticulum. Arch Biochem Biophys 1979; 198:434-8. [PMID: 42354 DOI: 10.1016/0003-9861(79)90517-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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2308
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Poole-Wilson PA, Bourdillon PD, Harding DP. Influence of contractile state on the size of the extracellular space in isolated ventricular myocardium. Basic Res Cardiol 1979; 74:604-10. [PMID: 121236 DOI: 10.1007/bf01907502] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A method is described with which the extracellular space of isolated ventricular muscle can be measured accurately and continuously in the same muscle. The size of the extracellular space is shown to vary with the contractile state of the myocardium. Interventions such as quiescence, manganese and acidosis reduce myocardial contractility and increase the size of the extracellular space. Barium, ouabain and hypoxia cause contracture and reduce the size of the extracellular space. These changes should be taken into account when measuring intracellular electrolytes in isolated ventricular preparations.
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2309
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Skov PS, Norn S, Weeke B. 3H-histamine release from human leukocytes. A new method for detecting type I allergy compared with basophil histamine release technique. Allergy 1979; 34:261-3. [PMID: 92898 DOI: 10.1111/j.1398-9995.1979.tb01707.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A rapid, simple, and inexpensive method for large scale screening of patients suspected of type I allergy has been developed. The method is based on in vitro incorporation of 3H-histamine in the leukocytes of the patient, whereafter release of labelled histamine is measured after provocation of the cells with the suspected allergen. The new method was compared with the conventional basophil histamine release technique by in vitro provocation of six asthmatic patients under suspicion of type I allergy against animal dander, house dust, and mite, and an almost identical release of histamine was observed in both assays.
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2310
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Mebs D, Gebauer E. Biologically active polypeptides from a sea anemone. Naturwissenschaften 1979; 66:207-8. [PMID: 35756 DOI: 10.1007/bf00366028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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2311
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Abstract
The mechanism of in vitro hyposensitization was examined in isolated rat mast cells. Surface distribution of immunoglobulin was examined by immunofluorescence technique. Hyposensitization could be ascribed neither to changes in the distribution of surface immunoglobulins nor to capping or shedding phenomena. The distribution of cell-bound antigen and the number of antigen-positive cells (patch-bearing cells) was not changed by hyposensitization. The binding of antigen to surface Ig was quantitated by I125-labelled antigen. In rats sensitized to two different antigens, hyposensitization of the mast cells with one of these inhibited the subsequent histamine release induced by either of the two antigens, whereas no changes were observed in the antigen binding capacity. The present investigation indicates that the mechanism of in vitro hyposensitization is the result of events secondary to the initial binding of antigen to the mast cell surface immunoglobulin.
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2312
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Abstract
Studies were performed on canine cardiac Purkinje fibers to evaluate the effects of acidosis and bicarbonate (HCO3) on action potential repolarization. Extracellular pH (pHe) was reduced from 7.4 to 6.8 by increasing carbon dioxide (CO2) concentration from 4 to 15% in a HCO3-buffered solution or by NaOH titration in a Hepes-buffered solution. Both types of acidosis produced a slowing of the rate of terminal repolarization (i.e., period of repolarization starting at about -60 mV and ending at the maximum diastolic potential) with an attendant increase in action potential duration of 10--20 ms. This was accompanied by a reduction in the maximum diastolic potential of 2--8 mV. In contrast, if the same pH change was made by keeping CO2 concentration constant and lowering extracellular HCO3 from 23.7 to 6.0 mM, in addition to the slowing of terminal repolarization, the plateau was markedly prolonged resulting in an additional 50- to 80-ms increase in action potential duration. If pHe was held constant at 7.4 and HCO3 reduced from 23.7 mM to 0 (Hepes-buffered solution), the changes in repolarization were nearly identical to those seen in 6.0 mM HCO3 except that terminal repolarization was unchanged. This response was unaltered by doubling the concentration of Hepes. Reducing HCO3 to 12.0 mM produced changes in repolarization of about one-half the magnitude of those in 6.0 mM HCO3. These findings suggest that in Purkinje fibers, HCO3 either acts as a current that slows repolarization or modulates the ionic currents responsible for repolarization.
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2313
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Donaldson SK, Hermansen L, Bolles L. Differential, direct effects of H+ on Ca2+ -activated force of skinned fibers from the soleus, cardiac and adductor magnus muscles of rabbits. Pflugers Arch 1978; 376:55-65. [PMID: 30066 DOI: 10.1007/bf00585248] [Citation(s) in RCA: 203] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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2314
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2315
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2316
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Abstract
1. The effects of decreasing pH from 7.40 to 6.20 on the tension developed by direct activation of the myofilaments and by Ca2+ release from the sarcoplasmic reticulum were studied comparatively in segments of single cells of skeletal muscle (frog semitendinosus) and cardiac muscle (rat ventricle) from which the sarcolemma had been removed by micro-dissection (skinned muscle cells). 2. The concentration of free Ca2+ in the solutions was buffered with ethylene glycol-bis (beta-aminoethylether N,N'-tetraacetic acid (EGTA). The change of the buffer capacity of a given [total EGTA] caused by varying pH and the uncertainty about the value of the equilibrium constant for Ca-EGTA have been taken into account in the interpretation of the results. 3. Decreasing pH from 7.40 to 6.20 produced an increase in the [free Ca2+] required for the myofilaments to develop 50% of the maximum tension by a factor of about 5 in skinned cardiac cells but of only 3 in skeletal muscle fibres. In addition, acidosis depressed the maximum tension developed in the presence of a saturating [free Ca2+] by approximately the same amount in the two tissues. 4. The pH optimum for loading the sarcoplasmic reticulum of skinned fibres from skeletal muscle decreased when the pCa (-log [free Ca2+]) in the loading solution decreased. The optimum was pH 7.40-7.00 for a loading at pCa 7.75, pH 7.00-6.60 at pCa 7.00 and pH 6.60-6.20 at pCa 6.00. 5. The pH optimum for loading the sarcoplasmic reticulum of skinned cardiac cells with a solution at pCa 7.75 was about pH 7.40 as in skeletal muscle fibres. But the cardiac sarcoplasmic reticulum could not be loaded with a [free Ca2+] much higher than pCa 7.75 because a higher [free Ca2+] triggered a Ca2+-induced release of Ca2+ from the sarcoplasmic reticulum. 6. The pH optimum of about 7.40 for the loading of the cardiac sarcoplasmic reticulum was also optimum for the Ca2+-induced release of Ca2+ from it. 7. It was concluded that the effects of acidosis on the cardiac sarcoplasmic reticulum accentuate the depressive action of decreasing pH on the myofilaments. This may explain the pronounced depression of contractility observed during acidosis in cardiac muscle. In contrast, a moderate acidosis causes an effect on skeletal muscle sarcoplasmic reticulum that could compensate for the depressive action on the myofilaments, which is, in addition, less pronounced than in cardiac muscle.
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2317
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de Castuma ES, Mattiazzi AR, Cingolani HE. Effect of hypercapnic acidosis on induction of arrhythmias by catecholamines in cat papillary muscles. Arch Int Physiol Biochim 1977; 85:509-18. [PMID: 72528 DOI: 10.3109/13813457709069868] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The effect of changes in PCO2 upon induction of arrhythmias in cat papillary muscles was studied. The average norepinephrine (NE) dose necessary to produce spontaneous contractions in muscles stimulated at rates of 10/min was higher at high PCO2. Whereas 2 100 +/- 295 X 10(-8) mol/litre of NE was necessary during acidosis, only 824 +/- 295 X 10(-8) mol/litre was necessary to produce spontaneous contractions in alkalosis. In quiescent muscles, the necessary doses in acidosis and alkalosis were 2 209 +/- 531 X 10(-8) and 518 +/- 159 X 10(-8) mol/litre respectively. With isoproterenol 458 +/- 84 X 10(-8) mol/litre was necessary to reach the end point at high PCO2, whereas only 131 +/- 52 X 10(-8) mol/litre was required at low PCO2. The lower sensitivity to catecholamine-induced arrhythmias with hypercapnic acidosis does not appear to be related to the re-uptake of the neurotransmitter by the nerve ending since it is also present with isoproterenol.
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2318
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2319
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Abstract
The effects of the ionophore X-537A on mechanical function and on ionic exchange were studied in the isolated, arterially perfused rabbit interventricular septum. X-537A produced an initial positive inotropic response which was, however, transient in this preparation and appeared to be dependent on an effect of the ionophore on catecholamines. The positive inotropy gave way to a progressive decline in force development which was unrelated to the action of catecholamines and was not accompanied by the development of contracture. Isotope uptake experiments revealed that coincident with this decline in force development there was a continuous net loss of tissue K+ and a net gain of Na+. X-537A (5 micronM) perfused for 20 minutes resulted in a net K+ loss of 50.2 +/- 4.6 mmol/kg dry weight and a net Na+ gain of 74.0 +/- 4.5 mmol/kg dry weight. Isotope washout experiments confirmed that the entire net loss of K+ could be accounted for by increased K+ efflux. X-537A did not alter Na+ efflux nor did it have any detectable effect on 45Ca exchange of the perfused septum in which the ability to detect net movements is at a level of approximately +/- 550 micron mol/kg dry weight. On removal of the ionophore the decline in force development ceased and reversed to near control levels and the progressive ionic changes ceased. However, despite the near total recovery of contractile function the Na+ and K+ levels remained at values little different from those reached at the termination of X-537A perfusion. In addition, after removal of the ionophore, we found that K+ exchange rate remained significantly less than control and, furthermore, a kinetic inhomogeneity of tissue K+ was observed. The results emphasize a dissociation between cellular Na+ and K+ content and function following the ionic perturbations induced by the ionophore.
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2320
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2321
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Abstract
Cardiac performance was assessed in 33 lambs less than 1 to 5 days of age by means of left ventricular function curves. Performance was quantified by determining stroke volume ejected at end diastolic pressure 10 cm H2O (SV10) with constant afterload. Coronary flow, myocardial O2 consumption (MVO2), blood gas tensions and pH were determined. Measurements were obtained before and at 30 min intervals following hemorrhage to 30 mm Hg arterial pressure, and in controls (arterial pressure 75 mm Hg). Effects of metabolic acidosis, hypercapnia and beta-blockade were determined. In control lambs acidosis and hypercapnia failed to reduce SV10 after two hours. In hemorrhaged animals both factors sharply reduced SV10 and lambs with prior beta-blockade showed no greater reduction. MVO2 fell following hemorrhage but did not differ with metabolic conditions and did not relate to SV10. It is concluded that beta-adrenergic function is critically important in preserving left ventricular performance in newborn exposed to acidosis or hypercapnia. With sustained hemorrhage this mechanism fails leading to a significant depression of ventricular function. MVO2 was not a determining factor in these studies.
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2322
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Kohlhardt M, Haap K, Figulla HR. Influence of low extracellular pH upon the Ca inward current and isometric contractile force in mammalian ventricular myocardium. Pflugers Arch 1976; 366:31-8. [PMID: 10549 DOI: 10.1007/bf02486557] [Citation(s) in RCA: 68] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In isolated papillary muscles of cats the changes in Ca inward current and isometric contractile force following a decrease of extracellular pH from 7.4 to 5.5 were studied. The Ca current was analyzed (a) by measuring the upstroke velocity of Ca-mediated action potentials and (b) in voltage clamp experiments using the double sucrose gap technique. 1. At a pH of 5.5 the upstroke velocity of the Ca-mediated action potential decreased to 65% of the control, while overshoot and action potential duration remained almost unchanged. Furthermore, the relative refractory period was prolonged and in some cases, a "Wenckebach-like" phenomenon occurred. In voltage clamp experiments, the slow inward current was found to be diminished to 50-60% of the initial control value and over a broad voltage range the current voltage relationship curve was shifted to weaker currents. Acidosis did not influence the steady state inactivation but altered the kinetics of inactivation of the slow inward current and induced an increase of tauinactivation and taurecovery. This indicates that acidosis exerts a complex effect on the slow membrane channel. 2. The normal response of the Ca current towards variations of the extracellular Ca concentration (0.5-4 mM) or towards the addition of the beta-stimulating compound isoproterenol (2 mg/l) was not altered by the lowered extracellular pH. 3. In the acid medium, isometric contractile force declined to 40% of the control value within 25 min and, thus, reacted stronger than the Ca current. This indicates that those forms of acidosis used in the present experiments caused their negative inotropic effect not exclusively via a depression of the Ca current. Rather an additional intracellular effect has to be assumed which finally leads to a reduced activity of the contractile system. 4. At pH 5.5 excess Ca (4 mM) induced the same quantitative response of the contractile system as obtained at normal pH. In contrast, the positive-inotropic effect of 2 mg/l isoproterenol was more pronounced, whilst the sensitivity of the Ca inward current towards this beta-stimulating compound remained unchanged.
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2323
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Abstract
There is no satisfactory explanation for the early and rapid decline of cardiac muscle function in ischaemia. Reduction of the energy source for contraction, A.T.P., is insufficient in magnitude and too slow in onset to be the prime cause. It is proposed that a large part of the loss of function is directly attributable to an immediate fall of intracellular pH and results from the accumulation of carbon dioxide and lactic acid; the intracellular acidosis reduces myocardial function by inhibition of that part of the calcium-ion influx associated with contraction.
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