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  • 1
    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
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    Paper (German National Licenses)
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  • 2
    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
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Enzyme-amplified enzyme-linked immunosorbent assay for gibberellin A4 based on the NAD-dependent redox cycle (1992)
    Springer
    Plant growth regulation 11 (1992), S. 391-396 
    Details
    ISSN: 1573-5087
    Keywords: Bulbil ; Dioscorea opposita ; ELISA ; gibberellin A4 ; immunoassay ; RIA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An antiserum against gibberellin A4 (GA4) raised in rabbits and its partially purified antibodies were used to develop radioimmunoassay (RIA) and indirect enzyme-linked immunosorbent assays (ELISAs) for GA4. Of three immunoassays tested, an ELISA based on the NAD-dependent redox cycle (enzyme-amplified ELISA) had highest sensitivity. Levels of methylated GA4 detected by this most sensitive method ranged from 0.1 fmol/assay (3.5 fg/assay) to 0.1 pmol/assay (3.5 pg/assay) suggesting applicability of this method to the detection of gibberellins in purified plant extracts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00130647
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    Paper (German National Licenses)
    Fulltext
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