Effect of cocaine and methylecgonidine on intracellular Ca2+ and myocardial contraction in cardiac myocytes

1997 ◽  
Vol 273 (2) ◽  
pp. H893-H901 ◽  
Author(s):  
L. Huang ◽  
J. H. Woolf ◽  
Y. Ishiguro ◽  
J. P. Morgan
Keyword(s):  
Structural Damage ◽  
Time Course ◽  
Crack Cocaine ◽  
Pyrolysis Product ◽  
Myocardial Contraction ◽  
Dependent Manner ◽  
Response Curves ◽  
Inotropic Effects ◽  
Cell Shortening ◽  
Dose Dependent

We evaluated the cardiac effects of the principle pyrolysis product of crack cocaine smoking, methylecgonidine (MEG), in comparison with cocaine. Peak cell shortening and intracellular Ca2+, as detected by the Ca2+ indicator indo 1, were recorded in enzymatically isolated ferret myocytes. Both cocaine and MEG decreased peak cell shortening and peak intracellular Ca2+ concentration ([Ca2+]i) in a dose-dependent manner (10(-8)-10(-4) M). MEG shifted the peak [Ca2+]i-to-peak shortening relationship downward and was more potent than cocaine. Atropine (10(-6) M) upwardly shifted the dose-response curves of MEG, cocaine, and carbachol but not of procaine. The negative inotropic effects of MEG were inhibited by methoctramine, a selective M2 receptor blocker but not by M1 (pirenzepine) or M3 (4-diphenylacetoxy-N-methylpiperidine methiodide) blocking agents. In contrast to cocaine, the effects of large doses of MEG were irreversible over the time course of our experiments, raising the possibility of structural damage. We conclude that MEG acts primarily on M2 cholinergic receptors in the heart to produce acute cardiac intoxication and, in contrast to cocaine, may decrease the myofilament Ca2+ responseness and cause structural damage to myocytes by a direct toxic effect.

Intracerebroventricular injection of prostaglandin E2 increases splenic sympathetic nerve activity in rats

1995 ◽  
Vol 269 (3) ◽  
pp. R662-R668 ◽  
Author(s):  
T. Ando ◽  
T. Ichijo ◽  
T. Katafuchi ◽  
T. Hori
Keyword(s):  
Prostaglandin E2 ◽  
Sympathetic Nerve ◽  
Time Course ◽  
Sympathetic Nerve Activity ◽  
Dependent Manner ◽  
Central Administration ◽  
Nerve Activity ◽  
High Doses ◽  
Alpha Chloralose ◽  
Dose Dependent

The effects of central administration of prostaglandin E2 (PGE2) and its selective agonists on splenic sympathetic nerve activity (SNA) were investigated in urethan- and alpha-chloralose-anesthetized rats. An intra-third-cerebroventricular (13V) injection of PGE2 (0.1-10 nmol/kg) increased splenic SNA in a dose-dependent manner. An I3V injection of an EP1 agonist, 17-phenyl-omega-trinor PGE2 (1-30 nmol/kg), also resulted in a dose-dependent increase in splenic SNA, with a time course similar to that of PGE2-induced responses. In contrast, EP2 agonists, butaprost (10-100 nmol/kg I3V) and 11-deoxy-PGE1 (10-100 nmol/kg I3V), had no effect on splenic SNA. An I3V injection of M & B-28767 (an EP3/EP1 agonist, EP3 >> EP1) increased splenic SNA only at high doses (10-100 nmol/kg). Pretreatment with an EP1 antagonist, SC-19220 (200 and 500 nmol/kg), completely blocked the responses of splenic SNA to PGE2 (0.1 nmol/kg) and M & B-28767 (10 nmol/kg), respectively. These findings indicate that brain PGE2 increases splenic SNA through its action on EP1 receptors.

Dose-response curves of effects of insulin on leucine kinetics in humans

1986 ◽  
Vol 251 (3) ◽  
pp. E334-E342 ◽  
Author(s):  
P. Tessari ◽  
R. Trevisan ◽  
S. Inchiostro ◽  
G. Biolo ◽  
R. Nosadini ◽  
...  
Keyword(s):  
Insulin Infusion ◽  
Leucine Incorporation ◽  
Dependent Manner ◽  
Carbon Oxidation ◽  
Response Curves ◽  
Leucine Kinetics ◽  
Dose Dependent ◽  
Kinetics In Vivo ◽  
Infusion Period

To determine the effects of physiological and pharmacological insulin concentrations on leucine-carbon kinetics in vivo, eight postabsorptive normal volunteers were infused with L-[4,5-3H]leucine and alpha-[1-14C]ketoisocaproate (KIC). Insulin concentrations were sequentially raised from 8 +/- 1 to 43 +/- 6 and 101 +/- 14 and to 1,487 +/- 190 microU/ml, while maintaining euglycemia with adequate glucose infusions. At the end of each 140-min insulin-infusion period, steady-state estimates of leucine and KIC rates of appearance (Ra), KIC (approximately leucine-carbon) oxidation, nonoxidized leucine-carbon flux [an index of leucine incorporation into protein (Leu----P)], and leucine and KIC interconversion rates were obtained. After the three insulin infusions, leucine Ra decreased by a maximum of approximately 20%. KIC Ra decreased by a maximum of approximately 50%. The sum of leucine plus KIC Ra in the basal state was 2.59 +/- 0.24 mumol X kg-1 X min-1 and decreased by approximately 30% at the maximal insulin concentrations. KIC oxidation decreased by a maximum of approximately 65%. Leu----P did not increase after hyperinsulinemia. Interconversion rates were promptly and markedly suppressed by 50-70%. Leucine clearance increased by approximately 120%. We conclude that euglycemic hyperinsulinemia, at physiological and pharmacological concentrations, decreased leucine and KIC concentrations, leucine-carbon turnover and oxidation, and leucine and KIC interconversions in a dose-dependent manner in vivo.

scholarly journals Endogenous H2S is required for hypoxic sensing by carotid body glomus cells

2012 ◽  
Vol 303 (9) ◽  
pp. C916-C923 ◽  
Author(s):  
Vladislav V. Makarenko ◽  
Jayasri Nanduri ◽  
Gayatri Raghuraman ◽  
Aaron P. Fox ◽  
Moataz M. Gadalla ◽  
...  
Keyword(s):  
Carotid Body ◽  
Time Course ◽  
Channel Blocker ◽  
Primary Site ◽  
Dependent Manner ◽  
Free Medium ◽  
Adult Rats ◽  
Glomus Cells ◽  
Dose Dependent ◽  
Carotid Body Glomus Cells

H2S generated by the enzyme cystathionine-γ-lyase (CSE) has been implicated in O2 sensing by the carotid body. The objectives of the present study were to determine whether glomus cells, the primary site of hypoxic sensing in the carotid body, generate H2S in an O2-sensitive manner and whether endogenous H2S is required for O2 sensing by glomus cells. Experiments were performed on glomus cells harvested from anesthetized adult rats as well as age and sex-matched CSE+/+ and CSE−/− mice. Physiological levels of hypoxia (Po2 ∼30 mmHg) increased H2S levels in glomus cells, and dl-propargylglycine (PAG), a CSE inhibitor, prevented this response in a dose-dependent manner. Catecholamine (CA) secretion from glomus cells was monitored by carbon-fiber amperometry. Hypoxia increased CA secretion from rat and mouse glomus cells, and this response was markedly attenuated by PAG and in cells from CSE−/− mice. CA secretion evoked by 40 mM KCl, however, was unaffected by PAG or CSE deletion. Exogenous application of a H2S donor (50 μM NaHS) increased cytosolic Ca2+ concentration ([Ca2+]i) in glomus cells, with a time course and magnitude that are similar to that produced by hypoxia. [Ca2+]i responses to NaHS and hypoxia were markedly attenuated in the presence of Ca2+-free medium or cadmium chloride, a pan voltage-gated Ca2+ channel blocker, or nifedipine, an L-type Ca2+ channel inhibitor, suggesting that both hypoxia and H2S share common Ca2+-activating mechanisms. These results demonstrate that H2S generated by CSE is a physiologic mediator of the glomus cell's response to hypoxia.

Effects of pinacidil on coronary Ca2+-myosin phosphorylation in cold potassium cardioplegia model

2000 ◽  
Vol 279 (3) ◽  
pp. H882-H888 ◽  
Author(s):  
Naruto Matsuda ◽  
Kathleen G. Morgan ◽  
Frank W. Sellke
Keyword(s):  
Time Course ◽  
Dependent Manner ◽  
Coronary Smooth Muscle ◽  
Intracellular Ca ◽  
No Signaling ◽  
Synthase Inhibitor ◽  
Mlc Phosphorylation ◽  
Dose Dependent ◽  
Cardioplegic Solutions

The effects of the potassium (K+) channel opener pinacidil (Pin) on the coronary smooth muscle Ca2+-myosin light chain (MLC) phosphorylation pathway under hypothermic K+cardioplegia were determined by use of an in vitro microvessel model. Rat coronary arterioles (100–260 μm in diameter) were subjected to 60 min of simulated hypothermic (20°C) K+cardioplegic solutions (K+= 25 mM). We first characterized the time course of changes in intracellular Ca2+concentration, MLC phosphorylation, and diameter and observed that the K+cardioplegia-related vasoconstriction was associated with an activation of the Ca2+-MLC phosphorylation pathway. Supplementation with Pin effectively suppressed the Ca2+accumulation and MLC phosphorylation in a dose-dependent manner and subsequently maintained a small decrease in vasomotor tone. The ATP-sensitive K+(KATP)-channel blocker glibenclamide, but not the nitric oxide (NO) synthase inhibitor Nω-nitro-l-arginine methyl ester, significantly inhibited the effect of Pin. K+cardioplegia augments the coronary Ca2+-MLC pathway and results in vasoconstriction. Pin effectively prevents the activation of this pathway and maintains adequate vasorelaxation during K+cardioplegia through a KATP-channel mechanism not coupled with the endothelium-derived NO signaling cascade.

Differential effect of vasopressin on angiotensin and norepinephrine pressor action in rats

1984 ◽  
Vol 247 (6) ◽  
pp. H973-H977 ◽  
Author(s):  
F. Elijovich ◽  
C. R. Barry ◽  
L. R. Krakoff ◽  
M. Kirchberger
Keyword(s):  
Heart Rate ◽  
Angiotensin Ii ◽  
Dependent Manner ◽  
Response Curves ◽  
Rightward Shift ◽  
Vasopressin Infusion ◽  
Dose Responses ◽  
Vascular Receptor ◽  
Dose Dependent ◽  
Mediated Reduction

The effect of vasopressin infusion on the pressor dose responses to angiotensin II and norepinephrine was studied in pentobarbital-anesthetized and unanesthetized nephrectomized rats. Pressor vasopressin (2–15 ng X kg-1 X min-1) given to anesthetized rats decreased sensitivity to angiotensin II in a dose-dependent manner (r = 0.88), an effect completely reversible by dPMeTyrAVP, a vasopressin vascular antagonist. Subpressor vasopressin (0.5-1 ng X kg-1 X min-1) given to unanesthetized rats diminished sensitivity to angiotensin II in the presence or absence of pentolinium (10 mg/kg). Shifts in dose-response curves to angiotensin II were always parallel. In contrast, dose responses to norepinephrine were not modified by vasopressin in pentolinium-treated rats and showed a small nonparallel rightward shift in animals without pentolinium. In animals without pentolinium, the baroreflex-mediated reduction in heart rate elicited by angiotensin II was not altered by vasopressin infusion. Our data suggest that vasopressin reduces angiotensin II pressor action by diminishing pressor sensitivity to the peptide. They indicate that the effect may be specific, mediated through the vascular receptor for vasopressin and independent of actions of this hormone on the autonomic nervous system.

scholarly journals Nesfatin-1 Suppresses Cardiac L-type Ca2+ Channels Through Melanocortin Type 4 Receptor and the Novel Protein Kinase C Theta Isoform Pathway

2015 ◽  
Vol 36 (2) ◽  
pp. 555-568 ◽  
Author(s):  
Jiaoqian Ying ◽  
Yuan Zhang ◽  
Shan Gong ◽  
Zhigang Chang ◽  
Xiaofeng Zhou ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Ventricular Myocytes ◽  
Dependent Manner ◽  
The Novel ◽  
Inotropic Effects ◽  
Kinase C ◽  
Melanocortin 4 Receptor ◽  
Dose Dependent ◽  
Ca2 Channels

Background/Aims: Nesfatin-1 (NF-1), an anorexic nucleobindin-2 (NUCB2)-derived hypothalamic peptide, acts as a peripheral cardiac modulator and it can induce negative inotropic effects. However, the mechanisms underlying these effects in cardiomyocytes remain unclear. Methods: Using patch clamp, protein kinase assays, and western blot analysis, we studied the effect of NF-1 on L-type Ca2+ currents (ICa,L) and to explore the regulatory mechanisms of this effect in adult ventricular myocytes. Results: NF-1 reversibly decreased ICa,L in a dose-dependent manner. This effect was mediated by melanocortin 4 receptor (MC4-R) and was associated with a hyperpolarizing shift in the voltage-dependence of inactivation. Dialysis of cells with GDP-β-S or anti-Gβ antibody as well as pertussis toxin pretreatment abolished the inhibitory effects of NF-1 on ICa,L. Protein kinase C (PKC) antagonists abolished NF-1-induced responses, whereas inhibition of PKA activity or intracellular application of the fast Ca2+-chelator BAPTA elicited no such effects. Application of NF-1 increased membrane abundance of PKC theta isoform (PKCθ), and PKCθ inhibition abolished the decrease in ICa,L induced by NF-1. Conclusion: These data suggest that NF-1 suppresses L-type Ca2+ channels via the MC4-R that couples sequentially to the βγ subunits of Gi/o-protein and the novel PKCθ isoform in adult ventricular myocytes.

Oxytocin-induced changes in single cell K+ currents and smooth muscle contraction of guinea-pig gastric antrum

1997 ◽  
Vol 136 (5) ◽  
pp. 531-538 ◽  
Author(s):  
Dessislava B Duridanova ◽  
Milena D Nedelcheva ◽  
Hristo S Gagov
Keyword(s):  
Smooth Muscle ◽  
Cell Membrane ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Gastric Antrum ◽  
Dependent Manner ◽  
Response Curves ◽  
Dose Dependent ◽  
In Cells

Abstract To study the effects of oxytocin on both spontaneous phasic contractions and K+ outward currents (IK) of the so-called 'non-target' smooth muscle cells, physiological concentrations of oxytocin ranging between 10−12 mol/l and 10−8 mol/l were applied to smooth muscle preparations and single voltage-clamped cells isolated from the circular layer of the guinea-pig gastric antrum. Oxytocin (10−12mol/l to 10−8 mol/l) suppressed, in a dose-dependent manner, the tetrodotoxin- and atropine-resistant spontaneous phasic contractions and shifted rightward the dose–response curves of 10−7 mol/l charybdotoxin and 10−3mol/l BaCl2. In cells with preloaded intracellular Ca2+ stores, oxytocin (10−12 mol/l to 10−9 mol/l) caused a dose-dependent activation of the charybdotoxin-blockable non-inactivating component of IK (IK(s1)) of single voltage-clamped cells, which was accompanied by hyperpolarization of the cell membranes. 8Lys-vasopressin and 8arg-vasopressin failed to mimic the effects of oxytocin on both contraction and K+ currents. Further, the oxytocin-induced activation of IK(s1) was effectively antagonized by 5× 10−8 mol/l U-73122 or 5× 10−6 mol/l 2-nitro-4-carboxyphenyl N,N-diphenylcarbamate (inhibitors of the cell membrane phospholipase C), as well as by intracellularly applied heparin (selective inhibitor of inositol-1,4,5-trisphosphate (IP3)-induced Ca2+ release channels). In cells incubated in the absence of Ca2+ entry throughout the study, oxytocin (10−9 mol/l) caused a slight and transient increase of IK(s1) amplitudes. Neither ryanodine (10−6 mol/l nor cyclopiazonic acid (10−6 mol/l) were able to restore the IK-activating effect of oxytocin in these cells. The data obtained suggest (i) that selective oxytocin receptors are present on the membranes of guinea-pig antral smooth muscle cells, (ii) that the oxytocin-related relaxation may result from the activation of Ca2+-sensitive K+ conductivity via activation of IP3-induced release of Ca from the submembrane located cisternae of the sarcoplasmic reticulum Ca2+ stores and (iii) in turn, this evokes a non-inactivating component of IK, hyperpolarizing the cell membrane. European Journal of Endocrinology 136 531–538

NH3 permeation through the apical membrane of MDCK cells is via a lipid pathway

1988 ◽  
Vol 255 (1) ◽  
pp. F135-F141
Author(s):  
K. Golchini ◽  
I. Kurtz
Keyword(s):  
Activation Energy ◽  
Acetic Acid ◽  
Plasma Membrane ◽  
Time Course ◽  
Apical Membrane ◽  
Mdck Cells ◽  
Disulfonic Acid ◽  
Dependent Manner ◽  
Cell Monolayers ◽  
Dose Dependent

The pathway for NH3 permeation across the apical membrane of MDCK cells was determined by measuring the effect of membrane fluidizing agents, protein reactive agents, and temperature on cellular NH3 influx. The rate of NH3 influx was calculated from the time course of increase in intracellular pH (pHi), measured with 2,7-biscarboxyethyl-5(6)-carboxyfluorescein, when MDCK cell monolayers were exposed to NH4Cl. The apical membrane NH3 permeability was 7.13 +/- 0.37 x 10(-3) cm/s (n = 12) at 37 degrees C and 1.23 +/- 0.07 x 10(-3) cm/s (n = 7) at 18 degrees C. In comparison, apical membrane permeability at 37 degrees C to the weak acids, valeric acid and acetic acid, were 1.39 +/- 0.11 x 10(-2) cm/s (n = 4) and 6.93 +/- 0.11 x 10(-3) cm/s (n = 4), respectively. The activation energy for NH3 permeation was 15.0 +/- 1.0 kcal/mol (17.5 degrees C-37.5 degrees C). In the presence of the membrane fluidizing agents, heptanol or chloroform, NH3 permeability increased in a dose-dependent manner. Heptanol (15 mM) significantly decreased the activation energy for NH3 permeation to 4.4 +/- 0.6 kcal/mol, P less than 0.001. The carboxyl reactive agent (1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide metho-p-toluensulfonic acid 1 mM), aminoreactive agents (4,4'-diisothiocyanostilbene-2,2'-disulfonic acid 50 microM; picrylsulphonic acid 1 mM), the sulphydryl reactive agent (p-chloromercuriphenylsulfonic acid 1 mM), and the nonspecific membrane protein cleaving agent pronase (1 mg/ml) had no effect on the NH3 influx. The results suggest that NH3 permeates the plasma membrane of MDCK cells via a lipid pathway.

Differential Modulation of the Cardiac L- and T-type Calcium Channel Currents by Isoflurane

2001 ◽  
Vol 95 (2) ◽  
pp. 515-524 ◽  
Author(s):  
Amadou K. S. Camara ◽  
Zeljana Begic ◽  
Wai-Meng Kwok ◽  
Zeljko J. Bosnjak
Keyword(s):  
Steady State ◽  
Calcium Channels ◽  
Reversal Potential ◽  
Calcium Currents ◽  
Dependent Manner ◽  
Inotropic Effects ◽  
Phenotypic Differences ◽  
Steady State Inactivation ◽  
Dose Dependent ◽  
Hyperpolarizing Shift

Background Volatile anesthetics exert their negative chronotropic and inotropic effects, in part by depressing the L- and T-type calcium channels. This study examines and compares the dose-dependent effects of isoflurane on atrial L- and T-type calcium currents (I(Ca,L) and I(Ca,T)) and ventricular I(Ca,L). Methods Whole cell I(Ca) was recorded from enzymatically isolated guinea pig cardiomyocytes. Current-voltage relations for atrial and ventricular I(Ca,L) was obtained from holding potentials of -90 and -50 mV to test a potential of +60 mV in 10-mV increments. Atrial I(Ca,T) was determined by subtraction of currents obtained from holding potentials of -50 and -90 mV. Steady state inactivation was determined using standard two-pulse protocols, and data were fitted with the Boltzmann equation. Results Isoflurane depressed I(Ca) in a dose-dependent manner, with Kd values of 0.23+/-0.03, 0.34+/-0.03, and 0.71+/-0.02 mM of anesthetic for atrial I(Ca,T) and I(Ca,L) and ventricular (ICa,L), respectively, and caused a significant (P < 0.05) hyperpolarizing shift in steady state inactivation. At 1.2 and 1.6 mm, isoflurane caused a significant (P < 0.05) depolarizing shift in the steady state activation in ventricular I(Ca,L) but not in atrial I(Ca,L) or I(Ca,T). In addition to the depression of I(Ca,L), isoflurane also induced a hyperpolarizing shift in the reversal potential of I(Ca) for both atrial and ventricular L-type calcium channels. Conclusion The results show that atrial I(Ca,T) is more sensitive to isoflurane than atrial I(Ca,L), and ventricular I(Ca,L) was the least responsive to the anesthetic. These differential sensitivities of the calcium channels in the atrial and ventricular chambers might reflect phenotypic differences in the calcium channels or differences in modulation by the anesthetic.

scholarly journals Electron Beam Irradiation Dose Dependently Damages theBacillusSpore Coat and Spore Membrane

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
S. E. Fiester ◽  
S. L. Helfinstine ◽  
J. C. Redfearn ◽  
R. M. Uribe ◽  
C. J. Woolverton
Keyword(s):  
Electron Beam ◽  
Structural Damage ◽  
Membrane Damage ◽  
Membrane Integrity ◽  
Effective Control ◽  
Spore Coat ◽  
Dependent Manner ◽  
Limited Data ◽  
Effective Electron ◽  
Dose Dependent

Effective control of spore-forming bacilli begs suitable physical or chemical methods. While many spore inactivation techniques have been proven effective, electron beam (EB) irradiation has been frequently chosen to eradicateBacillusspores. Despite its widespread use, there are limited data evaluating the effects of EB irradiation onBacillusspores. To study this,B. atrophaeusspores were purified, suspended in sterile, distilled water, and irradiated with EB (up to 20 kGy). Irradiated spores were found (1) to contain structural damage as observed by electron microscopy, (2) to have spilled cytoplasmic contents as measured by spectroscopy, (3) to have reduced membrane integrity as determined by fluorescence cytometry, and (4) to have fragmented genomic DNA as measured by gel electrophoresis, all in a dose-dependent manner. Additionally, cytometry data reveal decreased spore size, increased surface alterations, and increased uptake of propidium iodide, with increasing EB dose, suggesting spore coat alterations with membrane damage, prior to loss of spore viability. The present study suggests that EB irradiation of spores in water results in substantial structural damage of the spore coat and inner membrane, and that, along with DNA fragmentation, results in dose-dependent spore inactivation.

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