Abstract
We determined the effect of the dihydropyridine L-type Ca channel agonist BAY K 8644 (BAY) on excitation-contraction (E-C) coupling in isolated ferret ventricular myocytes using whole cell voltage clamp. The sarcoplasmic reticulum (SR) Ca load during the test pulses, assessed by caffeine-induced contractures, was similar in the presence and absence of BAY, with extracellular Ca concentration lowered from 3 to 1 mM in BAY. The relationship between L-type Ca current (I(Ca)) and contraction was assessed, with current and contractions measured during depolarizations from -40 to between -30 and +50 mV after a conditioning train (to ensure constant SR Ca load). BAY shifted the current-contraction relationship downward, such that, for a given I(Ca) and SR Ca load, the contraction elicited was much smaller in the presence of BAY. BAY also induced a characteristic negative shift in the current-voltage relationship. We conclude that BAY decreases the efficacy of a given Ca current to induce SR Ca release during E-C coupling in ferret cardiac tissue (in contrast to the BAY-induced increase of resting SR Ca release). This may reflect an alteration in the state of the SR Ca release channel due to BAY binding to dihydropyridine receptors.
Original language | English (US) |
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Journal | American Journal of Physiology - Cell Physiology |
Volume | 270 |
Issue number | 3 39-3 |
State | Published - Mar 1996 |
Externally published | Yes |
Keywords
- calcium current
- dihydropyridine
- ferret ventricular myocytes
- sarcoplasmic reticulum
ASJC Scopus subject areas
- Clinical Biochemistry
- Cell Biology
- Physiology
- Physiology (medical)