Abstract
It has been suggested that hypothyroidism may alter the responsiveness of the heart to sympathetic stimulation. To define more precisely the interrelationship between hypothyroidism and catecholamine responsiveness we: (a) studied the effects of norepinephrine and fluoride on the activation of adenyl cyclase in the particulate fraction of heart homogenates from euthyroid and hypothyroid cats; and (b) assessed the contractile response of isolated right ventricular papillary muscles from the same cats to increasing concentrations of norepinephrine. It was found that maximal accumulation of cyclic 3′,5′-adenosine monophosphate (3′,5′-AMP) was significantly lower at peak norepinephrine concentrations in the hypothyroid (284 ±5 pmoles) than in the euthyroid group (326 ±10 pmoles) (P < 0.02). However, the Km for norepinephrine was similar in both groups (1-2 × 10-5 moles/liter), and there was no apparent change in the threshold concentration. Fluoride-mediated increases in Cyclic 3′,5′-AMP accumulation were also significantly lower in the hypothyroid (585 ±25 pmoles) as compared to the euthyroid group (790 ±20 pmoles) (P < 0.02). In contrast, norepinephrine produced a similar augmentation of contractility in isolated papillary muscles from the hypothyroid and euthyroid cats. It thus appears that although the hypothyroid state is associated with a decrease in the total amount of myocardial adenyl cyclase per milligram of tissue capable of being activated by norepinephrine or fluoride, there is no change in the sensitivity of the enzyme to norepinephrine stimulation. Moreover, the finding that the inotropic response to norepinephrine is unaltered in hypothyroidism is compatible with the hypothesis that only a fraction of the total intracellular cyclic 3′,5′-AMP produced by norepinephrine activation of adenyl cyclase is required to elicit the inotropic response.
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- BENFORADO J. M., WIGGINS L. L. CONTRACTILITY, HEART RATE, AND RESPONSE TO NOREPINEPHRINE OF ISOLATED RAT MYOCARDIUM FOLLOWING I-131-INDUCED HYPOTHYROIDISM. J Pharmacol Exp Ther. 1965 Jan;147:70–75. [PubMed] [Google Scholar]
- Buccino R. A., Spann J. F., Jr, Pool P. E., Sonnenblick E. H., Braunwald E. Influence of the thyroid state on the intrinsic contractile properties and energy stores of the myocardium. J Clin Invest. 1967 Oct;46(10):1669–1682. doi: 10.1172/JCI105658. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Cheung W. Y., Williamson J. R. Kinetics of cyclic adenosine monophosphate changes in rat heart following epinephrine administration. Nature. 1965 Aug 28;207(5000):979–981. doi: 10.1038/207979b0. [DOI] [PubMed] [Google Scholar]
- Drummond G. I., Duncan L., Hertzman E. Effect of epinephrine on phosphorylase b kinase in perfused rat hearts. J Biol Chem. 1966 Dec 25;241(24):5899–5903. [PubMed] [Google Scholar]
- Grahame-Smith D. G., Butcher R. W., Ney R. L., Sutherland E. W. Adenosine 3',5'-monophosphate as the intracellular mediator of the action of adrenocorticotropic hormone on the adrenal cortex. J Biol Chem. 1967 Dec 10;242(23):5535–5541. [PubMed] [Google Scholar]
- HAMMERMEISTER K. E., YUNIS A. A., KREBS E. G. STUDIES ON PHOSPHORYLASE ACTIVATION IN THE HEART. J Biol Chem. 1965 Mar;240:986–991. [PubMed] [Google Scholar]
- Krishna G., Hynie S., Brodie B. B. Effects of thyroid hormones on adenyl cyclase in adipose tissue and on free fatty acid mobilization. Proc Natl Acad Sci U S A. 1968 Mar;59(3):884–889. doi: 10.1073/pnas.59.3.884. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Krishna G., Weiss B., Brodie B. B. A simple, sensitive method for the assay of adenyl cyclase. J Pharmacol Exp Ther. 1968 Oct;163(2):379–385. [PubMed] [Google Scholar]
- LEAK D., LEW M. Effect of treatment of hypothyroidism on circulatory response to adrenaline. Br Heart J. 1963 Jan;25:30–34. doi: 10.1136/hrt.25.1.30. [DOI] [PMC free article] [PubMed] [Google Scholar]
- LOWRY O. H., ROSEBROUGH N. J., FARR A. L., RANDALL R. J. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951 Nov;193(1):265–275. [PubMed] [Google Scholar]
- MURAD F., CHI Y. M., RALL T. W., SUTHERLAND E. W. Adenyl cyclase. III. The effect of catecholamines and choline esters on the formation of adenosine 3',5'-phosphate by preparations from cardiac muscle and liver. J Biol Chem. 1962 Apr;237:1233–1238. [PubMed] [Google Scholar]
- Margolius H. S., Gaffney T. E. The effects of injected norepinephrine and sympathetic nerve stimulation in hypothyroid and hyperthyroid dogs. J Pharmacol Exp Ther. 1965 Sep;149(3):329–335. [PubMed] [Google Scholar]
- Pastan I., Katzen R. Activation of adenyl cyclase in thyroid homogenates by thyroid-stimulating hormone. Biochem Biophys Res Commun. 1967 Dec 29;29(6):792–798. doi: 10.1016/0006-291x(67)90289-6. [DOI] [PubMed] [Google Scholar]
- Pool P. E., Sonnenblick E. H. The mechanochemistry of cardiac muscle. I. The isometric contraction. J Gen Physiol. 1967 Mar;50(4):951–965. doi: 10.1085/jgp.50.4.951. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Robison G. A., Butcher R. W., Oye I., Morgan H. E., Sutherland E. W. The effect of epinephrine on adenosine 3', 5'-phosphate levels in the isolated perfused rat heart. Mol Pharmacol. 1965 Sep;1(2):168–177. [PubMed] [Google Scholar]
- SCHNECKLOTH R. E., KURLAND G. S., FREEDBERG A. S. Effect of variation in thyroid function on the pressor response to norepinephrine in man. Metabolism. 1953 Nov;2(6):546–555. [PubMed] [Google Scholar]
- SUTHERLAND E. W., RALL T. W., MENON T. Adenyl cylase. I. Distribution, preparation, and properties. J Biol Chem. 1962 Apr;237:1220–1227. [PubMed] [Google Scholar]
- Sutherland E. W., Robison G. A. The role of cyclic-3',5'-AMP in responses to catecholamines and other hormones. Pharmacol Rev. 1966 Mar;18(1):145–161. [PubMed] [Google Scholar]
- Taunton O. D., Roth J., Pastan I. Studies on the adrenocorticotropic hormone-activated adenyl cyclase of a functional adrenal tumor. J Biol Chem. 1969 Jan 25;244(2):247–253. [PubMed] [Google Scholar]
- WURTMAN R. J., KOPIN I. J., AXELROD J. Thyroid function and the cardiac disposition of catecholamines. Endocrinology. 1963 Jul;73:63–74. doi: 10.1210/endo-73-1-63. [DOI] [PubMed] [Google Scholar]
- van der Schoot J. B., Moran N. C. An experimental evaluation of the reputed influence of thyroxine on the cardiovascular effects of catecholamines. J Pharmacol Exp Ther. 1965 Sep;149(3):336–345. [PubMed] [Google Scholar]