Effects of diltiazem upon a rapidly exchanging calcium compartment related to repriming in frog skeletal muscle
| ISSN: |
1573-2657
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| Source: |
Springer Online Journal Archives 1860-2000
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| Topics: |
Biology
Medicine
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| Notes: |
Summary Following spontaneous relaxation, fast skeletal muscle must first repolarize and then undergo a first-order repriming reaction before depolarization will result in maximal tension production. 45Ca exposure during repriming defined two Ca compartments during subsequent efflux, named Cafast and Caslow. Caslow had an average time constant of 112±17 min. On the basis of slow turnover and content determined by a variety of methods, I suggest Caslow represents Ca within the sarcoplasmic reticulum. Cafast contained 12 pmol Ca per fibre and resting exchange had a time constant of 5.1±0.4 min. A total of 12 pmol 45Ca within Cafast was released during a maximal contracture. Most of the Ca released from Cafast rapidly entered the extracellular space; however, 0.39±0.15 pmol Ca per fibre transferred from Cafast into Caslow when the muscle bundle contracted. When 1–10 μM diltiazem reduced contracture time-tension, release of Cafast was reduced proportionally. When 10 μM diltiazem paralyzed excitation-contraction coupling, Cafast was not released. Refilling of Cafast was proportional to the extent of repriming during 45Ca exposure. Although release and refilling of Cafast is related to contraction, its role in excitation-contraction coupling remains to be elucidated.
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| Type of Medium: |
Electronic Resource
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| URL: |