ISSN:
1432-2013
Keywords:
Adrenaline
;
cAMP-dependent protein kinase
;
Slow inward calcium current
;
Inotropy
;
K outward current
;
Transient inward current
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Cyclic adenosine 3′,5′-monophosphate (cAMP) or the free catalytic subunit (C) of the cAMP-dependent protein kinase were pressure injected into single guinea pig ventricular cells. The following results were obtained: 1. Injection of cAMP prolonged the action potential and shifted the action potential plateau to a more positive level. Under voltage clamp, cAMP injection increased the amplitude of the slow inward calcium current (I si). 2. Injection of C permanently prolonged the action potential and enhanced the amplitude ofI si by a factor of 2–4, depending on the amount of injected C. In the current-voltage relations the potential of maximumI si and the apparent current reversal did not change. 3. After maximum prolongation of the action potential due to repeated injections of C, even high concentrations of adrenaline did not further change the configuration of the action potential. 4. In many experiments transient depolarizations appeared after the injection. Correspondingly, under voltage clamp transient inward currents occurred. 5. C injection increased both the time-dependent and time-independent potassium outward current. 6. In response to injection of the catalytic subunit, the isotonic contraction was larger in amplitude and relaxation was faster. It is concluded that the cAMP-dependent protein kinase increases the slow inward calcium current in the heart, presumably by phosphorylation of some membrane proteins.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00581064
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