Ventricular fibrillation is reduced in hypothyroid rats with enhanced myocardial α-adrenoceptor responsiveness

R. Chess-Williams, S. J. Coker

Research output: Contribution to journalArticleResearchpeer-review

13 Citations (Scopus)

Abstract

The severity of ventricular arrhythmias induced by coronary artery occlusion and reperfusion has been examined in control rats and animals made hypothyroid by pretreatment with 6-propylthiouracil (PTU). The maximal driving frequency and sensitivity of isolated left atria and papillary muscles to isoprenaline and to phenylephrine in the presence of propranolol, were also examined in tissues from control and hypothyroid animals. Pretreatment with PTU resulted in a potentiation of responses to the α-adrenoceptor agonist phenylephrine in both left atria and papillary muscles, while responses to isoprenaline were depressed in left atria but unaltered in papillary muscles from hypothyroid animals. In rats subject to coronary artery occlusion, PTU pretreatment reduced the incidence of ventricular fibrillation during acute myocardial ischaemia and abolished reperfusion-induced ventricular fibrillation. Mortality during myocardial ischaemia and reperfusion was also abolished. Diastolic blood pressure was similar in hypothyroid and control animals, but there was a small reduction in systolic blood pressure and a marked decrease in heart rate in PTU pretreated animals. These results demonstrate that PTU-induced hypothyroidism represents a condition where cardiac α-adrenoceptor-mediated responses are enhanced but the severity of ischaemia- and reperfusion-induced arrhythmias is reduced.

Original languageEnglish
Pages (from-to)95-100
Number of pages6
JournalBritish Journal of Pharmacology
Volume98
Issue number1
DOIs
Publication statusPublished - 1 Jan 1989
Externally publishedYes

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Propylthiouracil
Ventricular Fibrillation
Adrenergic Receptors
Papillary Muscles
Heart Atria
Blood Pressure
Myocardial Reperfusion
Coronary Occlusion
Phenylephrine
Isoproterenol
Reperfusion
Myocardial Ischemia
Cardiac Arrhythmias
Coronary Vessels
Hypothyroidism
Propranolol
Ischemia
Heart Rate
Mortality
Incidence

Cite this

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title = "Ventricular fibrillation is reduced in hypothyroid rats with enhanced myocardial α-adrenoceptor responsiveness",
abstract = "The severity of ventricular arrhythmias induced by coronary artery occlusion and reperfusion has been examined in control rats and animals made hypothyroid by pretreatment with 6-propylthiouracil (PTU). The maximal driving frequency and sensitivity of isolated left atria and papillary muscles to isoprenaline and to phenylephrine in the presence of propranolol, were also examined in tissues from control and hypothyroid animals. Pretreatment with PTU resulted in a potentiation of responses to the α-adrenoceptor agonist phenylephrine in both left atria and papillary muscles, while responses to isoprenaline were depressed in left atria but unaltered in papillary muscles from hypothyroid animals. In rats subject to coronary artery occlusion, PTU pretreatment reduced the incidence of ventricular fibrillation during acute myocardial ischaemia and abolished reperfusion-induced ventricular fibrillation. Mortality during myocardial ischaemia and reperfusion was also abolished. Diastolic blood pressure was similar in hypothyroid and control animals, but there was a small reduction in systolic blood pressure and a marked decrease in heart rate in PTU pretreated animals. These results demonstrate that PTU-induced hypothyroidism represents a condition where cardiac α-adrenoceptor-mediated responses are enhanced but the severity of ischaemia- and reperfusion-induced arrhythmias is reduced.",
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Ventricular fibrillation is reduced in hypothyroid rats with enhanced myocardial α-adrenoceptor responsiveness. / Chess-Williams, R.; Coker, S. J.

In: British Journal of Pharmacology, Vol. 98, No. 1, 01.01.1989, p. 95-100.

Research output: Contribution to journalArticleResearchpeer-review

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