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  • 1
    ISSN: 1432-1912
    Keywords: Key words SHR ; Endothelium-dependent relaxation ; Rat mesenteric vascular bed ; Rat thoracic aorta ; Bradykinin Acetylcholine ; Age dependency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The present study examined whether alterations of endothelium-dependent vasorelaxation in spontaneously hypertensive rats (SHR) in response to the endothelium-dependent vasodilators acetylcholine and bradykinin ran parallel. We tried to find out the age at which endothelium-dependent vasorelaxation in response to each agonist became impaired and compared three different groups of SHR aged 7, 21 and 51 weeks. To be able to separate hypertension-induced alterations from age-dependent changes age-matched normotensive Wistar rats were included. Endothelium-dependent vasorelaxation was studied in the mesenteric vascular bed precontracted with noradrenaline, a typical resistance vessel, which showed relaxation to both acetylcholine and bradykinin, and the precontracted thoracic aorta, which only responded to acetylcholine. There were major differences in the agonist-dependent vasorelaxation between bradykinin and acetylcholine in SHR as a function of age. A surprising finding was that acetylcholine-induced relaxation was preserved, even slightly improved not only in young SHR (7 weeks) with developing hypertension but also in adult SHR (21 weeks) with established hypertension, which can be interpreted as a compensatory mechanism. As expected, in old SHR (51 weeks) acetylcholine-induced vasorelaxation was impaired as a consequence of the detrimental effects of long-term hypertension on endothelium. The parallel changes observed with acetylcholine in the mesenteric vascular bed and thoracic aorta provided mutual confirmation. In clear contrast to acetylcholine bradykinin-induced vasorelaxation was already impaired in young SHR with developing hypertension suggesting that bradykinin-induced vasorelaxation is either much more sensitive to detrimental effects of (even slightly) increased blood pressure or, more likely, that there is a basic deficiency in the action of bradykinin in SHR. Thus, our study allows to conclude that impairment of acetylcholine-induced endothelium-dependent vasorelaxation in the mesenteric vascular bed of SHR is a secondary phenomenon developing as a consequence of long-term hypertension while the impaired bradykinin-induced vasorelaxation seems to be a primary phenomenon that could be closely related to the development of hypertension.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: dv/dt of Ventricular Pressure Curve of the Heart ; dp/dt of Ventricular Pressure Curve ; Performance of the Heart ; Metabolic Alcalosis ; Pressure Load ; Increased Preload ; dv/dt der Ventrikeldruckkurve des Herzens ; dp/dt der Ventrikeldruckkurve ; Herzarbeit ; Herzleistung ; metabolische Alkalose ; Druckarbeit ; Füllungsdruckerhöhung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Es wurden Untersuchungen am isolierten Katzenherzen mit der Fragestellung durchgeführt, obdp/dt max unddv/dt max der Druckkurve des linken Ventrikels mit Parameters korrelieren, die sich nicht primär aus der Druckkurve ergeben. Besonders interessierten dabei mögliche Beziehungen zu Arbeit und Leistung des linken Ventrikels. Durch metabolische Alkalose (pH 7,8) erhöhte Druckbelastung und Füllungsdruckerhöhung wurden Dynamik und somit physikalisches Resultat der Systole verändert. Ohne Berücksichtigung dieser unterschiedlichen Versuchsbedingungen ergab sich für jeden Versuch eine gesicherte Korrelation zwischendv/dt max und Arbeit bzw. Leistung des linken Ventrikels. Dagegen ließen sich solche Korrelationen zum Schlag-bzw. Herzzeitvolumen und zur Beschleunigungsarbeit nicht nachweisen. Werden die entsprechenden Korrelationen für die genannten Versuchsbedingungen getrennt untersucht, so besteht teilweise eine Beziehung zwischendv/dt max und Schlag-, Herzzeitvolumen bzw. Beschleunigungsarbeit. dp/dt max hängt in ähnlicher Weise von Arbeit und Leistung des linken Ventrikels ab, es ergaben sich jedoch teilweise kleinere Korrelationskoeffizienten. Aus den Ergebnissen läßt sich eine Proportionalität zwischendv/dt max als wesentlichem dynamischen Parameter der Druckarbeit des Ventrikels und dem physikalischen Resultat seiner Systole ableiten.
    Notes: Summary Experiments were performed at isolated cat hearts to examine correlations betweendp/dt max ordv/dt max of the ventricular pressure curve and stroke volume, cardiac index, 1/2 mv2 and performance of the left ventricle. By metabolic alcalosis, pressure load and increased preload the dynamics of ventricular contraction and its physical result were varied. Each heart showed an exact correlation betweendv/dt max and the physical work of the left chamber per systole, respectively performance. Controversely, there could not be found correlations betweendv/dt max and stroke volume, cardiac index and 1/2 mv2. By separate examination of these correlations at metabolic alcalosis, pressure load or increased preload, there exists a particular dependence ofdv/dt max from these parameters. However, the dependence ofdv/dt max from left ventricular work per systole is unchanged. Similar correlations were found betweendp/dt max and the left ventricular work per systole. It is concluded that there exists a proportionality betweendv/dt max as the most important derivation of the ventricular pressure curve and the physical result of ventricular contraction.
    Type of Medium: Electronic Resource
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