Korean J Physiol Pharmacol.  1998 Dec;2(6):733-742.

Increase of L-type calcium current by cGMP-dependent protein kinase regulates in rabbit ventricular myocytes

• Han J
• Kim N
• Kim E
• Ho W
• Earm YE
• Kim H

Abstract

BACKGROUND: We have previously reported that not only cGMP but also 8-Br-cGMP or 8-pCPT-cGMP, specific and potent stimulators of cGMP-dependent protein kinase (cGMP-PK), increased basal L-type calcium current (ICa) in rabbit ventricular myocytes. Our findings in rabbit ventricular myocytes were entirely different from the earlier findings in different species, suggesting that the activation of cGMP-PK is involved in the facilitation of ICa by cGMP. However, there is no direct evidence that cGMP-PK can stimulate ICa in rabbit ventricular myocytes. In this report, we focused on the direct effect of cGMP-PK an ICa in rabbit ventricular myocytes.
METHODS AND RESULTS
We isolated single ventricular myocytes of rabbit hearts by using enzymatic dissociation. Regulation of ICa by cGMP-PK was investigated in rabbit ventricular myocytes using whole-cell voltage clamp method. ICa was elicited by a depolarizing pulse to +10 mV from a holding potential of -40 mV. Extracellular 8-(4-Chlorophenylthio)-guanosine-3',5'-cyclic monophosphate (8-pCPT-cGMP), potent stimulator of cGMP-dependent protein kinase (cGMP-PK), increased basal ICa. cGMP-PK also increased basal ICa. The stimulation of basal ICa by cGMP-PK required both 8-Br-cGMP in low concentration and intracellular ATP to be present. The stimulation of basal ICa by cGMP-PK was blocked by heat inactivation of the cGMP-PK and by bath application of 8-(4-chlorophenylthio)-guanosine-3',5'-cyclic monophosphate, Rp-isomer (Rp-pCPT-cGMP), a phosphodiesterase-resistant cGMP-PK inhibitor. When ICa was increased by internal application of cGMP-PK, IBMX resulted in an additional stimulation of ICa. In the presence of cGMP-PK, already increased ICa was potentiated by bath application of isoprenaline or forskolin or intracellular application of cAMP.
CONCLUSIONS
We present evidence that cGMP-PK stimulated basal ICa by a direct phosphorylation of L-type calcium channel or associated regulatory protein in rabbit ventricular myocytes.

Keyword

cGMP-dependent protein kinase (cGMP-PK); L-type calcium current (ICa); Rabbit ventricular myocytes; Whole-cell voltage clamp

MeSH Terms

1-Methyl-3-isobutylxanthine
Adenosine Triphosphate
Baths
Calcium Channels, L-Type
Calcium*
Colforsin
Heart
Hot Temperature
Isoproterenol
Muscle Cells*
Phosphorylation
Protein Kinases*
1-Methyl-3-isobutylxanthine
Adenosine Triphosphate
Calcium
Calcium Channels, L-Type
Colforsin
Isoproterenol
Protein Kinases