Abstract
In isolated electrically driven (1.0 Hz, 37°C) left atria of normal rats (NR) as well as of those made hypothyroid (HR) by feeding with propylthiouracil the β-sympathomimetic effects of isoprenaline (IPN) and of phenylephrine (PE) in the presence of 10−5M yohimbine on force of contraction and on the cAMP-level were investigated. In HR the dose-response curves for the positive inotropic effects (PIE) of IPN and PE were shifted to the right in comparison to NR; thus, the pD2-value for IPN was significantly decreased from 8.39±0.07(N=8) to 7.99±0.1(N=4), that for PE from 5.44±0.08(N=5) to 4.93±0.08 (N=9). In NR a submaximal effective concentration (EC80 for the PIE) of IPN(3 × 10−8M) increased the cAMP-level after 60sec by about 60%; in HR, however, the same concentration produced only a 25% increase in cAMP. The EC80 for the PIE of PE(10−5M) increased in NR the cAMP-level by approximately 35%, but failed to increase it in HR. When used in three times higher concentrations, however, both agents produced in HR an increase of the cAMP-level comparable with the effects in NR.
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© 1978 Springer-Verlag Berlin Heidelberg
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Brodde, OE., Schümann, H.J., Wagner, J. (1978). Decreased Sensitivity of β-Adrenoceptors in Left Atria from Hypothyroid Rats. In: Deutsche Pharmakologische Gesellschaft. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-662-39532-5_100
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DOI: https://doi.org/10.1007/978-3-662-39532-5_100
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-662-38666-8
Online ISBN: 978-3-662-39532-5
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