GLORIA

GEOMAR Library Ocean Research Information Access

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
  • 1
    Electronic Resource
    Electronic Resource
    Sensitivity changes of adrenergic β-receptors induced by alterations of the metabolic state of isolated organs (1972)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 275 (1972), S. 105-113 
    Details
    ISSN: 1432-1912
    Keywords: Sympathomimetic Affinity ; β-Receptors ; Temperature ; Metabolic State ; Isolated Organs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experiments on isolated organs-rabbit ileum, guinea-pig trachea and atrium — with different “β-receptor subtypes” were carried out in order to determine whether changes of the metabolic state or of the extracellular pH were able to alter the responsiveness of these receptors to sympathomimetic amines. 1. Guinea-Pig Atrium. Lowering of the pH of the bath fluid from 7.48 to 6.79 resulted in a significant decrease of the affinity of isoprenaline (IPN) calculated as the pD2-value. Metabolic inhibition induced by iodoacetic acid (IAA) (5×10−5 M) increased the affinity of Th 1165a. 2. Rabbit Ileum. The affinity of IPN was not changed by lowering the pH, even to values of 6.11. At this pH the spontaneous motility was already markedly impaired. IAA (2.4×10−5 M) caused a moderate increase in the affinity of IPN whereas those of Th 1165a and orciprenaline (OPN) were elevated 10-fold. 3. Guinea-Pig Trachea. Lowering of the pH caused a decrease of the pD2-values of IPN and in particular of Th 1165a. The metabolic inhibitor IAA had no influence upon the pD2 value of IPN. 4. The present results favour the existence of only one type of β-receptor which changes its sensitivity depending on the metabolic state. It seems therefore very likely that the affinity of sympathomimetic drugs depends not only on the structure of the β-receptor but also on the metabolic state of the tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00505071
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Influence of the metabolic state on the action of phenylephrine on rabbit ileum, guinea-pig vas deferens and atrium (1973)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 276 (1973), S. 63-70 
    Details
    ISSN: 1432-1912
    Keywords: Isolated Organs ; Adrenergic α- and β-Receptors ; Temperature ; Metabolic Inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Under the conditions of altered temperature or metabolic inhibition experiments have been carried out on isolated organs with adrenergic α- and β-receptors, i.e., on rabbit ileum and guinea-pig vas deferens and atrium. Using phenylephrine as a selective α-adrenergic stimulant we were interested to determine whether or not an alteration of the metabolic conditions was capable of causing changes in the affinity of phenylephrine which were identical for the α- and β-receptors. 1. Rabbit Ileum. At 25°C the affinity of phenylephrine to the inhibitory adrenergic α-receptors was 100 times higher than to the β-receptors. Its affinity to the α-receptors was not influenced by raising the temperature or inhibiting the metabolic rate by iodoacetic acid (IAA), whereas that to the β-receptors was diminished to a great extent by raising the temperature. Preincubation at 42°C with the metabolic inhibitor IAA increased the affinity to β-receptors so that it was similar to that at 25°C. 2. Vas Deferens. The excitatory α-mimetic effect of phenylephrine was similarly unaltered by raising the temperature of the bath from 25° to 42°C. IAA did not affect responses to phenylephrine. 3. Guinea-Pig Atrium. An increase of the temperature from 25° to 42°C significantly decreased the affinity of phenylephrine to the β-receptors, whereas IAA at 42°C increased it almost to control values at 25°C. 4. The experiments show that the sensitivity of α-receptors is not altered by an increase of temperature irrespective of whether the α-receptors are mediating inhibitory or excitatory effects, whereas that of the β-receptors is depressed. These results favour the hypothesis that stimulation of α-receptors is independent of, while that of the β-receptors is strongly dependent on the metabolic rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500779
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Positive inotropic effects of phenylephrine in the isolated rabbit papillary muscle mediated both by α-and β-adrenoceptors (1974)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 284 (1974), S. 133-148 
    Details
    ISSN: 1432-1912
    Keywords: Adrenoceptors ; Phenylephrine ; Phosphodiesterase Inhibitors ; Rabbit Papillary Muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary On the isolated papillary muscle of the rabbit experiments were performed in order to study whether β-and/or α-adrenoceptors mediate the positive inotropic effect of phenylephrine and, for comparison, of other sympathomimetic drugs. 1. The positive inotropic effect of phenylephrine in concentrations of up to 3×10−6M was antagonized by the α-adrenolytic drug phentolamine, while that evoked by higher concentrations was inhibited by the β-adrenolytic drug pindolol. The intrinsic activity of phenylephrine amounted to 0.6 compared with that of isoprenaline. 2. Pretreatment with reserpine altered neither the pD2-value for phenylephrine nor its intrinsic activity. 3. The inhibitors of phosphodiesterase, theophylline (10−4M) and papaverine (10−5M) enhanced the effect of higher concentrations of phenylephrine—mediated mainly by stimulation of β-adrenoceptors, whereas that of lower concentrations—mediated by stimulation of α-adrenoceptors—was not affected. Papaverine strongly increased the intrinsic activity of phenylephrine, which then reached that of isoprenaline. 4. The α-adrenoceptor stimulating drugs, methoxamine, naphazoline and oxymetazoline did not cause positive inotropic effects but, on the contrary, negative ones. The positivei notropic effect of noradrenaline was not changed by phentolamine, whereas that of adrenaline in concentrations of up to 10−5 M was inhibited. 5. From these results it is concluded that in the rabbit papillary muscle not only β- but also α-adrenoceptors are of functional importance for the mediation of the positive inotropic effect of some sympathomimetic drugs. The nature of these α-adrenoceptors is apparently distinct from those of other organs since these receptors were stimulated only by phenylephrine and adrenaline but not by noradrenaline, methoxamine, naphazoline and oxymetazoline.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00501118
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Beta-adrenolytic, antiarrhythmic and local anaesthetic effects of phenylephrine (1974)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 284 (1974), S. 245-261 
    Details
    ISSN: 1432-1912
    Keywords: Phenylephrine ; Isolated Organs ; Competitive Dualism in Action ; Local Anaesthesia ; Antiarrhythmic Activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The β-sympathomimetic effect of phenylephrine was investigated on the electrically driven atrium, as well as on the tracheal chain of the guinea pig. 1. Phenylephrine (PE) was found to be less effective than isoprenaline (IPN) with regard to its positive inotropic effect on the guinea-pig atrium and to its relaxing action on the tracheal chain. The intrinsic activity for PE amounted to 0.75 on the tracheal chain and to 0.45 on the atrium, when compared with IPN. 2. From these low intrinsic activities, PE was assumed to be a partial β-agonist, exerting a competitive dualism in action to IPN. This dualism could be confirmed by dose-response curves for PE in the presence of IPN and vice versa: PE behaved as a β-agonist as well as a β-antagonist. 3. The intrinsic activity of PE steadily decreased with prolongation of the incubation period. After 1 h PE had almost lost its intrinsic activity. Under these conditions the dose-response curves for IPN on the tracheal chain, as well as on atrium, were shifted to the right in a parallel manner, i.e. PE behaved as a competitive β-antagonist. 4. High concentrations of PE (10−3 M) protected the electrically driven guineapig atrium against arrhythmias induced by k-strophanthoside. The onset of both the first extrasystoles and of heart standstill, which occurred after infusion of k-strophanthoside, were delayed after preincubation with PE. 5. Phentolamine was without any influence on these antiarrhythmic properties of PE. Therefore, it could be excluded that the antiarrhythmic effect of phenylephrine is due to a stimulation of myocardial α-adrenoceptors. 6. The local anaesthetic activity of phenylephrine, as tested on the rabbit cornea, was 4 times higher than that of propranolol. 7. The effective concentrations for the β-adrenolytic, antiarrhythmic, and local anaesthetic activities of PE were clearly different. We concluded, therefore, that the different actions produced by phenylephrine were not associated with each other.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500345
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Influence of temperature on the positive inotropic effects mediated by α- and β-adrenoceptors in the isolated rabbit papillary muscle (1975)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 287 (1975), S. 61-72 
    Details
    ISSN: 1432-1912
    Keywords: α-Adrenoceptors ; Frequency-Force Relationship ; Temperature ; D600 ; Rabbit Papillary Muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary On the isolated rabbit papillary muscle experiments were carried out to determine whether the positive inotropic effects mediated by α- and by β-adrenoceptors are brought about by different mechanisms or not.—For this reason the influence of temperature and the effect of the calcium antagonist D600 on the responses to phenylephrine and to isoprenaline were compared. 1. The maximal inotropic effects of phenylephrine, isoprenaline and calcium were not affected by raising the temperature of the organ bath from 37° to 42°C whereas the basal developed tension of the muscle was significantly decreased. 2. The dose-response curve for phenylephrine was markedly shifted to the right by raising the temperature (ΔpD 2=0.89), while that for isoprenaline was also shifted to the right, but to a lesser extent (ΔpD 2=0.23). 3. In the presence of 1.5 × 10−8M pindolol the shift of the dose-response curve for phenylephrine induced by elevation of temperature was more prominent (ΔpD 2=1.91), whereas phentolamine (3 × 10−6M) inhibited the temperatureinduced shift. 4. The positive inotropic effect of phenylephrine—mediated by α-adrenoceptors under blockade of β-adrenoceptors by 1.5 × 10−8M pindolol—was markedly depressed by D600 (10−7 and 3 × 10−7M): the dose-response curve was shifted to the right and the maximal response was depressed. On the other hand, the positive inotropic effect of isoprenaline—mediated by β-adrenoceptors—was affected to a lesser extent by D600 and the maximal response was not changed. 5. These results indicate that the stimulation of α-adrenoceptors in the rabbit papillary muscle induces a positive inotropic response through a biochemical process different from that caused via β-adrenoceptors, i.e., stimulation of α-adrenoceptors may increase the intracellular calcium level mainly by changing the transmembrane calcium flux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00632638
    Location Call Number Limitation 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...