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  • 1
    Electronic Resource
    Electronic Resource
    Thyroid hormone modulates inotropic responses, α-adrenoceptor density and catecholamine concentrations in the rat heart (1996)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 354 (1996), S. 755-764 
    Details
    ISSN: 1432-1912
    Keywords: Key words Calcium handling ; α1-adrenoceptors ; Hyperthyroidism ; Hypothyroidism ; Tissue ; catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We investigated the influence of hyper- and hypothyroidism on basal parameters of isolated perfused hearts of rats. In addition the effects of different extracellular calcium concentrations ([Ca2+]o), the calcium entry promoter Bay K8644 and the α1-adrenoceptor agonist methoxamine were investigated. Since alterations in α-adrenoceptor density could explain the increased sensitivity to methoxamine in hearts from hypothyroid rats, α1-adrenoceptor density in the left ventricle was also established. Different time-schedules of exposure to hyper- and hypothyroidism were used to investigate whether the influence of chronic dysthyroid states on α1-adrenoceptor density is transient and time-dependent. Simultaneously myocardial noradrenaline and adrenaline tissue concentrations were determined, since they might correlate with the observed changes. Hyperthyroidism was induced by feeding rats for 1, 4 and 8 weeks with 5 mg/kg L-thyroxine (T4)- containing rat chow. Hypothyroid rats were obtained by adding 0.05% propylthiouracil (PTU) to the drinking water during 1, 4 and 8 weeks. For the functional experiments animals were treated during 4 weeks, to mimic the clinical situation of a chronic endocrine disease. Langendorff hearts from hyperthyroid hearts showed an increased maximally developed relaxation velocity, whereas Langendorff hearts from hypothyroid rats showed an increased left ventricular pressure (LVP). We observed an increased maximal inotropic response to [Ca2+]o in hearts from both hyperthyroid and hypothyroid rats, indicating that both dysthyroid states interfere with the handling of calcium ions by the contractile apparatus. Unchanged responses to Bay K8644 in hearts from hyperthyroid and depressed responses in hearts from hypothyroid rats suggest that the involvement of L-type calcium channels is rather unlikely. Furthermore, the reflex increase in coronary flow in response to enhanced contractile force appeared to fail in hearts from hypothyroid rats. Sensitivity of the response to methoxamine was increased in hearts from hypothyroid rats, which was accompanied by a decrease in the number of myocardial α1-adrenoceptors. Both T4 and PTU treatment resulted in a non-transient decrease of α1-adrenoceptor density in left ventricular tissue. Furthermore, hypothyroidism increased the percentage of α1A-binding sites, whereas in hyperthyroidism the distribution of the α1-adrenoceptor subtypes was not affected. Myocardial tissue concencentrations of noradrenaline and adrenaline were unchanged in hyperthyroid rats and decreased in hypothyroid rats. The present study indicates that thyroid hormones have a direct rather than a sympathetically mediated effect on α1-adrenoceptor mediated myocardial functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166902
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Thyroid hormone modulates inotropic responses, α-adrenoceptor density and catecholamine concentrations in the rat heart (1996)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 354 (1996), S. 755-764 
    Details
    ISSN: 1432-1912
    Keywords: Calcium handling ; α1-adrenoceptors ; Hyperthyroidism ; Hypothyroidism ; Tissue catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We investigated the influence of hyper- and hypothyroidism on basal parameters of isolated perfused hearts of rats. In addition the effects of different extracellular calcium concentrations ([Ca2+]o), the calcium entry promoter Bay K8644 and the α1-adrenoceptor agonist methoxamine were investigated. Since alterations in α-adrenoceptor density could explain the increased sensitivity to methoxamine in hearts from hypothyroid rats, α1-adrenoceptor density in the left ventricle was also established. Different time-schedules of exposure to hyper- and hypothyroidism were used to investigate whether the influence of chronic dysthyroid states on α1-adrenoceptor density is transient and time-dependent. Simultaneously myocardial noradrenaline and adrenaline tissue concentrations were determined, since they might correlate with the observed changes. Hyperthyroidism was induced by feeding rats for 1, 4 and 8 weeks with 5 mg/kg L-thyroxine (T4)-containing rat chow. Hypothyroid rats were obtained by adding 0.05% propylthiouracil (PTU) to the drinking water during 1, 4 and 8 weeks. For the functional experiments animals were treated during 4 weeks, to mimic the clinical situation of a chronic endocrine disease. Langendorff hearts from hyperthyroid hearts showed an increased maximally developed relaxation velocity, whereas Langendorff hearts from hypothyroid rats showed an increased left ventricular pressure (LVP). We observed an increased maximal inotropic response to [Ca2+]o in hearts from both hyperthyroid and hypothyroid rats, indicating that both dysthyroid states interfere with the handling of calcium ions by the contractile apparatus. Unchanged responses to Bay K8644 in hearts from hyperthyroid and depressed responses in hearts from hypothyroid rats suggest that the involvement of L-type calcium channels is rather unlikely. Furthermore, the reflex increase in coronary flow in response to enhanced contractile force appeared to fail in hearts from hypothyroid rats. Sensitivity of the response to methoxamine was increased in hearts from hypothyroid rats, which was accompanied by a decrease in the number of myocardial α1-adrenoceptors. Both T4 and PTU treatment resulted in a non-transient decrease of α1-adrenoceptor density in left ventricular tissue. Furthermore, hypothyroidism increased the percentage of α1A-binding sites, whereas in hyperthyroidism the distribution of the α1-adrenoceptor subtypes was not affected. Myocardial tissue concencentrations of noradrenaline and adrenaline were unchanged in hyperthyroid rats and decreased in hypothyroid rats. The present study indicates that thyroid hormones have a direct rather than a sympathetically mediated effect on α1-adrenoceptor mediated myocardial functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166902
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Angiotensin II-induced increase in slowly exchanging 45Ca2+ in relation to contractile responses of rat and guinea-pig aorta (1991)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 344 (1991), S. 107-113 
    Details
    ISSN: 1432-1912
    Keywords: 45Ca2+ ; Angiotensin II ; Calcium entry blockers ; Rat aorta ; Guinea-pig aorta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To gain more information about sources of activator Ca2+ involved in the contraction of rat and guinea-pig aorta evoked by angiotensin II and their sensitivity to Ca 2+ entry blockers, measurement of slowly exchanging 45Ca2+ was established. A more physiological procedure was used, replacing La3+- and EGTA- containing solutions by a normal Ca2+-containing buffer. It was demonstrated that the angiotensin 11-induced increase in slowly exchanging 45Ca2+ in rat aorta was incompletely (by approximately 60%–70%) inhibited by the organic Ca2+ entry blockers nifedipine, verapamil and diltiazem and by other Ca+ entry blocking compounds like CoCl2 and chlorpromazine. 8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8) was able to inhibit the angiotensin II-induced increase in 45Ca2+ content completely, but this may be an intracellular storage effects. By contrast, the organic Ca2+ entry blockers completely inhibited that part of the angiotensin II-induced contraction of rat aorta which was dependent upon extracellular Ca2+. In guinea-pig aorta, the increase in 45Ca2+ content elicited by angiotensin 11 could be completely suppressed by all compounds under study. The results of these experiments correlated well with data from the functional experiments in guinea-pig aorta. In both preparations the release of Ca 2+ from a rapidly as well as a slowly exchanging intracellular pool appears to contribute to the contractile response elicited by angiotensin 11.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167389
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Lack of relationship between intrinsic activity and susceptibility of pressor responses to blockade by nifedipine among the α2 agonists B-HT 920 and B-HT 958 (1984)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 327 (1984), S. 90-92 
    Details
    ISSN: 1432-1912
    Keywords: B-HT 920 ; B-HT 958 ; Postjunctional vascular α2-adrenoceptors ; Partial and full agonism ; Calcium entry blockade
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Following i.v. bolus injections into pithed normotensive rats, the maximal diastolic pressor responses to B-HT 920 and B-HT 958 amounted to 115 and 35 mm Hg, respectively. Prazosin (0.1 mg/kg, i.v.,-15 min) was without effect on the log dose-pressor effect curve of B-HT 958, whereas yohimbine (1 mg/kg, i.v.,-15 min) shifted this curve about 30-fold to the right, showing the exclusive participation of α2-adrenoceptors in the vasoconstrictor response to B-HT 958. In doses of 10 and 30 mg/kg, B-HT 958 displaced the log dose-vasoconstrictor effect curve of B-HT 920 approximately 6- and 30-fold, respectively, to the right, illustrating the partial agonism of B-HT 958 at postjunctional vascular α2-adrenoceptors. Despite the marked difference in intrinsic activity of B-HT 920 and B-HT 958, the calcium entry blocker nifedipine exhibited a comparable inhibitory action on the vasopressor responses to both agonists. This finding indicates that partial and full agonism at vascular α2-adrenoceptors are not related to the susceptibility of the initiated pressor response to inhibition by calcium entry blockade.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00504998
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Abstracts of papers pharmacological meeting (1987)
    Springer
    Pharmacy world & science 9 (1987), S. 291-301 
    Details
    ISSN: 1573-739X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01953632
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  • 6
    Electronic Resource
    Electronic Resource
    Abstracts of papers pharmacological meeting (1985)
    Springer
    Pharmacy world & science 7 (1985), S. 228-236 
    Details
    ISSN: 1573-739X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02307582
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Abstracts of papers pharmacological meeting (1986)
    Springer
    Pharmacy world & science 8 (1986), S. 270-278 
    Details
    ISSN: 1573-739X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01960072
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
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