-transparent.png){kind=logo}
BACKGROUND Many of the cardiovascular manifestations of thyroid hormone excess resemble those produced by sympathoadrenal stimulation. The objective of this study was to determine the effects of thyroid hormone excess on myocardial beta-adrenergic expression and responsiveness to infused agonists in the primate heart. RESULTS The responses of left ventricular isovolumic contraction (dP/dt(max)) and relaxation (tau) during graded dobutamine infusion were studied both before and after 4 weeks of thyroid hormone administration in 8 chronically instrumented baboons. At matched (atrially paced) heart rates, thyroid hormone significantly increased resting dP/dt(max) (3073+/-1034 versus 2318+/-829 mm Hg/s, P<.05) and decreased tau (24.0+/-5.5 versus 28.2+/-5.4 ms, P<.05). The change from baseline for dP/dt(max) and tau in response to beta1-adrenergic stimulation was significant at each dobutamine dose (2.5 to 10 microg x kg(-1) x min(-1)), but when expressed as a percent change, it was similar before versus after thyroid hormone. Similar changes were found when beta2-adrenergic stimulation was produced by terbutaline infusion in three additional baboons. beta-Adrenergic receptor (betaAR) expression was higher in five thyroxine-treated than in five control baboons (37.4+/-1.2 versus 15.7+/-3.2 fmol/mg, P<.001), and this was due to a greater increase in the beta2AR (5.9+/-1.5 to 20.6+/-1.2 fmol/mg, P<.001) than the beta1AR (9.7+/-1.7 to 16.8+/-0.1 fmol/mg, P<.01) subtype. CONCLUSIONS In the primate heart, thyroid hormone produces positive inotropic and lusitropic effects in the resting state and upregulates both beta1AR and beta2AR, with the beta2AR increase predominating. At equivalent rates, however, thyroid hormone excess does not appear to enhance the sensitivity of left ventricular contractility and relaxation to either beta1- or beta2-adrenergic stimulation.
B D Hoit, and
S F Khoury, and
Y Shao, and
M Gabel, and
S B Liggett, and
R A Walsh
March 1987,
The American journal of physiology,
B D Hoit, and
S F Khoury, and
Y Shao, and
M Gabel, and
S B Liggett, and
R A Walsh
February 1984,
Life sciences,
B D Hoit, and
S F Khoury, and
Y Shao, and
M Gabel, and
S B Liggett, and
R A Walsh
May 1986,
The American journal of physiology,
B D Hoit, and
S F Khoury, and
Y Shao, and
M Gabel, and
S B Liggett, and
R A Walsh
May 1992,
Pediatric research,
B D Hoit, and
S F Khoury, and
Y Shao, and
M Gabel, and
S B Liggett, and
R A Walsh
August 1984,
Life sciences,
B D Hoit, and
S F Khoury, and
Y Shao, and
M Gabel, and
S B Liggett, and
R A Walsh
February 2000,
Metabolism: clinical and experimental,
B D Hoit, and
S F Khoury, and
Y Shao, and
M Gabel, and
S B Liggett, and
R A Walsh
April 1981,
Hormone and metabolic research = Hormon- und Stoffwechselforschung = Hormones et metabolisme,
B D Hoit, and
S F Khoury, and
Y Shao, and
M Gabel, and
S B Liggett, and
R A Walsh
January 1983,
Clinical and experimental pharmacology & physiology,
B D Hoit, and
S F Khoury, and
Y Shao, and
M Gabel, and
S B Liggett, and
R A Walsh
January 1981,
Mechanisms of ageing and development,
B D Hoit, and
S F Khoury, and
Y Shao, and
M Gabel, and
S B Liggett, and
R A Walsh
October 1976,
Canadian journal of physiology and pharmacology,
