Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Adenosine  (3)
  • Negative inotropic effect  (2)
  • [3H]prazosin binding  (2)
  • 5-Methylurapidil  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Phorbol ester does not mimic, but antagonizes the alpha-adrenoceptor-mediated positive inotropic effect in the rabbit papillary muscle (1988)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 337 (1988), S. 169-176 
    Details
    ISSN: 1432-1912
    Keywords: Phorbol ester ; Protein kinase C ; alphaAdrenoceptors ; beta-Adrenoceptors ; Positive inotropic effects ; Phenylephrine ; [3H]prazosin binding ; [3H]CGP-12177 binding ; Rabbit papillary muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) was used to examine the hypothesis that phosphoinositide turnover is involved in the regulation of myocardial contractility mediated by stimulation of alpha-adrenoceptors in the mammalian cardiac muscle. Exposure of the isolated rabbit papillary muscle electrically driven at a rate of 1 Hz at a temperature of 37°C to TPA in concentrations of 10–1000 nmol/l for 30 min did not affect the basal force of contraction. The concentration-response curve for the positive inotropic effect of (−)-phenylephrine mediated by stimulation of alpha-adrenoceptors in the presence of (±)-bupranolol (100 nmol/1) was shifted to the right and downward by TPA in concentrations of 30–1000 nmol/l, while the effect of (−)-phenylephrine mediated by stimulation of beta-adrenoceptors in the presence of prazosin (100 nmol/l) was not decreased, but slightly enhanced by exposure of the muscle to relatively low concentrations of TPA (10–100 nmol/l). Incubation of the membrane fraction isolated from the rabbit ventricular muscle with TPA in vitro under the same condition as employed in the physiological experiments decreased the specific binding of [3H]prazosin but not that of [3H]CGP-12177, while the non-tumor promoting phorbol ester, αPDD, was ineffective. These results indicate that activation of protein kinase C by TPA does not mimic the positive inotropic effect of catecholamines mediated by activation of myocardial alpha-adrenoceptors. on the other hand, the specific interaction of alpha-adrenoceptor-mediated processes with TPA in the rabbit papillary muscle is in line with the view that the facilitation of phosphoinositide turnover and subsequent activation of protein kinase C may play a certain role in the coupling of alpha-adrenoceptor occupation by agonists to the process leading to the positive inotropic action.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169245
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Potent inhibitory action of chlorethylclonidine on the positive inotropic effect and phosphoinositide hydrolysis mediated via myocardial alpha1-adrenoceptors in the rabbit ventricular myocardium (1991)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 343 (1991), S. 669-673 
    Details
    ISSN: 1432-1912
    Keywords: Chlorethylclonidine ; Alpha1-adrenoceptors ; Positive inotropic effect ; [3H]prazosin binding ; Phosphoinositide hydrolysis ; Rabbit papillary muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of the alphalb-adrenoceptor-selective antagonist chlorethylclonidine on the alpha1-adrenergic positive inotropic effect and the phosphoinositide hydrolysis induced by phenylephrine was investigated in the rabbit ventricular myocardium. Pretreatment of membrane fractions derived from the rabbit ventricular muscle with 10−5 mol/l chlorethylclonidine decreased the specific binding of [3H]prazosin (at a saturating concentration of 10−9 mol/l) from the control value of 11.27±0.48 to 4.18±1.87 fmol/mg protein. The inhibition by adrenaline of the binding of [3H]prazosin (slope factor and affinity) was not affected by chlorethylclonidine. The positive inotropic effect of phenylephrine (in the presence of 3 × 10−7 mol/l bupranolol) was inhibited by chlorethylclonidine in a concentration-dependent manner (10−7−10−5 mol/l) and abolished by 10−5 mol/l chlorethylclonidine. The concentration of chlorethylclonidine to inhibit the phenylephrine-induced maximum response to 50% was 2.4 × 10−6 mol/l. The accumulation of [3H]inositol monophosphate and [3H]inositol trisphosphate induced by 10−5 mol/l phenylephrine was inhibited by chlorethylclonidine in the same concentration range. These findings indicate that the myocardial alpha1-adrenoceptors mediating a positive inotropic effect in the rabbit ventricular myocardium may belong to the chlorethylclonidine-sensitive alpha1b-subtype, and that the subcellular mechanism of action involve phosphoinositide hydrolysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00184301
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Pharmacological characteristics of adenosine-induced inhibition of dog ventricular contractility: dependence on the pre-existing level of β-adrenoceptor activation (1991)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 344 (1991), S. 70-78 
    Details
    ISSN: 1432-1912
    Keywords: Adenosine ; Phenylisopropyladenosine ; Negative inotropic effect ; Cyclic AMP ; Ventricular myocardium of the dog
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experiments were carried out to characterize the adenosine-induced negative inotropic effect in relation to the extent of β-adrenoceptor activation in the isolated dog left ventricular myocardium. Adenosine and R-N6-phenylisopropyladenosine inhibited the positive inotropic effect of isoprenaline (10−7 mol/1 and lower) about 20% of its maximal response, which was antagonized by an A1 adenosine receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine in a concentration-dependent manner. The negative inotropic effect of adenosine disappeared and that of R-N6-phenylisopro-pyl-adenosine decreased when the isoprenaline concentration was elevated to the level higher than 10−7 mol/1. Adenosine deaminase (1.5 U/ml) that abolished the negative inotropic effect of adenosine enhanced the effect of R-N6-phenylisopropyladenosine, indicating that endogenous adenosine released by high isoprenaline concentration (10−6 mol/1) modulates the interaction. The maximal response to adenosine and R-N6-phenylisopro-pyladenosine determined in the presence of 10−7 mol/1 isoprenaline was 50% of that of carbachol which elicited the maximal inhibition even in the presence of 10−6 mol/1 isoprenaline. The negative inotropic effects of R-N6-phenylisopropyladenosine and carbachol were additive to the maximal response equivalent to that of carbachol. The difference in the efficiency between the adenosine and muscarinic receptor agonists may be partly ascribed to the difference in densities of the respective receptors in the dog ventricular myocardium. The negative inotropic effect of R-N6-phenylisopropyladenosine in the presence of isoprenaline was associated with decrease in cyclic AMP levels elevated previously by isoprenaline. The elevation of cyclic AMP levels caused by isoprenaline (3 × 10−7 mol/1) was abolished by R-N6-phenylisopro-pyladenosine (10−4 mol/1), while the contractile response was reduced only by 30% with R-N6-phenylisopro-pyladenosine. In the absence of β-adrenoceptor stimulation R-N6-phenylisopropyladenosine elicited a negative inotropic effect without changes in cyclic AMP levels, but this effect was less than 10% of the basal force of contraction. It is concluded that in the dog ventricular myocardium adenosine receptors play a role for the inhibitory regulation of contractility, which is influenced markedly by the pre-existing level of β-adrenoceptor activation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167384
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Acetylcholine and adenosine activate the G protein-gated muscarinic K+ channel in ferret ventricular myocytes (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 351 (1995), S. 610-617 
    Details
    ISSN: 1432-1912
    Keywords: Ferret ; Ventricular myocytes ; Acetylcholine ; Adenosine ; Muscarinic K+ ; channel ; G protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The properties of the K+ channel activated by acetylcholine (ACh) and adenosine (Ado) were examined in single ferret ventricular myocytes using patch-clamp techniques. In the whole-cell configuration, ACh and Ado induced an inwardly rectifying K+ current and shortened the action potential duration. The effect of ACh was blocked by atropine, while the Ado effect was interrupted by 8-cyclopenty1,1,2-dipropyl xanthine, a specific Ado A1 receptor antagonist. In cell-attached recordings, ACh and Ado added to the pipette solution activated a single population of inwardly rectifying K+ channels, distinct from the i K1 channel. The channel had a slope conductance of ∼ 40 pS in symmetrical 150 mM K+ solutions and a mean open time of 0.8 ms. Excision of the patch into the inside-out patch configuration in guanosine triphosphate (GTP)-free solution abolished the channel activity. The channel was reversibly reactivated by adding GTP to the intracellular side of the patch. GTPγS activated the channel irreversibly. When the inside-out patch was treated with the A protomer of pertussis toxin (PTX), intracellular GTP no longer activated the K+ channel. The results show that ferret ventricular myocytes possess a K+ channel activated by both muscarinic and Ado A1 receptors. Its electrophysiological properties and the gating by a PTX-sensitive G protein in a membrane-delimited fashion are identical with those of the muscarinic K+ channels in nodal and atrial tissues of other species. In conclusion, the G protein-gated muscarinic K+ channel is expressed in ferret ventricular myocardium and may underlie the direct negative inotropism of ACh and Ado in this tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170160
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Pronounced direct inhibitory action mediated by adenosine A1 receptor and pertussis toxin-sensitive G protein on the ferret ventricular contraction (1993)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 348 (1993), S. 282-289 
    Details
    ISSN: 1432-1912
    Keywords: Adenosine ; Phenylisopropyladenosine ; Adenosine receptors ; Negative inotropic effect ; G proteins ; Ferret ventricular myocardium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An adenosine A1 receptor agonist R-N6-phenylisopropyladenosine (R-PIA) elicited a pronounced negative inotropic effect with the EC50 value of 0.69 μmol/1 in the presence of a β-adrenoceptor blocking agent bupranolol (0.3 μmol/1) in the isolated ferret papillary muscle. The negative inotropic effect of R-PIA was not associated with changes in cyclic AMP level. Adenosine and other A1 receptor agonists also elicited a negative inotropic effect. DPCPX (1,3-dipropyl-8-cyclopentyl xanthine) antagonized the negative inotropic effect of R-PIA in a competitive manner (pA2 value = 8.4). The inhibitory action of R-PIA was markedly attenuated in the ventricular muscle preparation isolated from ferrets pretreated with pertussis toxin that caused ADP-ribosylation of 39 kDa proteins in the membrane fraction. In the membrane fraction derived from the ferret ventricle, [3H]-DPCPX bound to a single binding site in a saturable and reversible manner with high affinity (Kd value = 1.21±0.41 nmol/l; B max = 12.8±3.02 fmol/mg protein; n = 7). The binding characteristics of [3H]-DPCPX in the rat ventricle (Kd value = 1.51 ±0.09 nmol/l; B max = 12.7±1.47 fmol/mg protein; n = 5) were similar to those in the ferret. On the other hand, the content of Go, a major pertussis toxin-sensitive G protein in the ferret heart, was much higher in the ferret than in the rat ventricle. The present results indicate that adenosine receptors may play an important role in the inhibitory regulation of ventricular contractility in the ferret in contrast to other mammalian species. The signal transduction process subsequent to agonist binding to A1 receptors including the pertussis toxin-sensitive G protein and ion channels may be responsible for the unique inhibitory action of adenosine in this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169157
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Role of alpha1A adrenoceptor subtype in production of the positive inotropic effect mediated via myocardial alpha, adrenoceptors in the rabbit papillary muscle: influence of selective alpha1A subtype antagonists WB 4101 and 5-methylurapidil (1992)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 345 (1992), S. 578-585 
    Details
    ISSN: 1432-1912
    Keywords: WB 4101 ; 5-Methylurapidil ; Alpha1 adrenoceptors ; Positive inotropic effect ; [3H]CGP-12177 ; Rabbit papillary muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to elucidate the contribution of alpha1A subtype to the positive inotropic effect mediated by myocardial alpha, adrenoceptors, the influence of the alpha1A selective antagonists WB 4101 and 5-methylurapidil on the alpha,-mediated positive inotropic effect (induced by phenylephrine in the presence of a beta adrenoceptor blocking agent bupranolol) was assessed in the isolated rabbit papillary muscle. WB 4101 (10−9-10−7mol/l) shifted the concentration-response curve of the alpha,-mediated positive inotropic effect to the right in parallel, but the slope of Schild plot did not meet the competitive antagonism: WB 4101 shifted the curve by log one unit at 10−9 mol/1, whereas it did not cause further shift at higher concentrations of 10−8 and 10−7 mol/l. WB 4101 did not affect the beta adrenoceptor-mediated positive inotropic effect. 5-Methylurapidil (10−9 to 10−7 mol/l) shifted the curve of alpha1-mediated positive inotropic effect to the right and downwards in a concentration-dependent manner; the slope of Schild plot calculated at the level of 20% of the maximum response to phenylephrine was close to unity. 5-Methylurapidil at 3 × 10−7 mol/1 abolished the alpha1-mediated positive inotropic effect. In addition, 5-methylurapidil inhibited the beta adrenoceptor-mediated positive inotropic effect in the same concentration range as it antagonized the alpha1-mediated positive inotropic effect, indicating that 5-methylurapidil is not selective for myocardial alpha, adrenoceptors. In the membrane fraction derived from the rabbit ventricular muscle, 5-methylurapidil displaced the specific binding of [3H]CGP-12177 with high affinity, whereas WB 4101 did not affect the [3H]CGP-12177 binding in the concentration range that it antagonized the alpha,-mediated positive inotropic effect. The present results indicate that alpha1A adrenoceptor subtype plays a role in production of the positive inotropic effect mediated by myocardial alpha, adrenoceptors, but the extent is less than that mediated by alpha1B subtype in the rabbit ventricular myocardium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00168952
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...