Triiodothyronine-induced changes in function, metabolism and weight of the rat heart: effects of alpha- and beta-adrenergic blockade.
The involvement of alpha- and beta-adrenergic receptors in the triiodothyronine (T3)-induced hemodynamic and metabolic alterations and in the development of cardiac hypertrophy was analyzed in time-course studies. Female Sprague-Dawley rats received daily injections of T3 (200 micrograms/kg s.c.) and a continuous i.v. infusion of 0.9% NaCl or alpha- or beta-receptor blocking agents. NaCl-injected animals served as controls. Eighteen hours after T3 administration, heart rate and LV dP/dtmax were considerably elevated. Cardiac output (CO) was not significantly changed. These alterations were abolished by simultaneous infusion of the beta-adrenergic blocker metoprolol. After 48 hours, CO as well as the cardiac RNA concentration were markedly elevated. The rise in LV dP/dtmax and heart rate was similar to the 18-h-value and was prevented by metoprolol. However, metoprolol did not influence the increase in CO and RNA concentration. Likewise, after 72 hours, metoprolol antagonized the T3-induced increase in heart rate and LV dP/dtmax, but had no effect on the elevation of CO and RNA concentration, the enhancement of adenine nucleotide synthesis and cardiac hypertrophy. Like metoprolol, the alpha-adrenergic blocker prazosin did not influence the T3-evoked cardiac hypertrophy. Thus, the development of cardiac hypertrophy in this model can occur independently of alpha- and beta-adrenergic stimulation.
Zierhut
W
W
Department of Physiology, University of München, FRG.
Zimmer
H G
HG
D000818:Animals; D002302:Cardiac Output; D006332:Cardiomegaly / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology*; D004247:DNA / Q000032:analysis; D005260:Female; D006321:Heart / Q000187:drug effects / Q000503:physiopathology*; D006339:Heart Rate; D006439:Hemodynamics / Q000187:drug effects; D008055:Lipids / Q000032:analysis; D008790:Metoprolol / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D011224:Prazosin / Q000494:pharmacology; D012313:RNA / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013997:Time Factors; D014284:Triiodothyronine / Q000494:pharmacology*
D008055:Lipids; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D014284:Triiodothyronine; D012313:RNA; D004247:DNA; D008790:Metoprolol; D011224:Prazosin