| Autor: |
SKELTON, C. LYNN, SU, JUDY Y., POOL, PETER E. |
| Zdroj: |
Cardiovascular Research; May1976, Vol. 10 Issue 3, p380-384, 5p |
| Abstrakt: |
The mechanism responsible for the enhancement of myocardial contractility in hyperthyroidism is unclear. The possibility that this mechanism may involve a direct effect on the contractile proteins was investigated using the glycerol-extracted muscle strip from right ventricular papillary muscles of euthyroid rabbits and rabbits made hyperthyroid by the intraperitoneal injection of 0.25 mg/kg 1-thyroxine for 10 d. Intact papillary muscles from the hyperthyroid rabbits had an enhanced rate of tension development, a decreased time to peak tension, and a slight though insignificant increase in active tension compared to control animals. Maximal isometric contractions were induced in glycerol-extracted cardiac muscle strips from the two animal groups by the addition of 5 mmol/litre ATP and 5 mmol/litre MgCl in a buffer solution containing 0.15 mol/litre Tris-HCl (pH 7.1) at 26°C. Peak isometric tension was increased in glycerinated muscle strips from hyperthyroid rabbits (1.52±0.10 vs 1.26±0.13 g/mm2), but the differences did not reach statistical significance. However, there was a marked increase in the rate of tension development in the hyperthyroid group (62.5±5.4 vs 41.8±4.7 mg·mm−2/s, P<0.01). This increase in the rate of isometric tension development in both intact and glycerinated muscles from hyperthyroid rabbits may be related to changes in the intrinsic turnover of actomyosin cross-bridge links in this condition. Thus, these findings suggest that thyroid hormone may influence cardiac muscle function by a direct effect on the contractile proteins. [ABSTRACT FROM PUBLISHER] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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