Cyclic GMP regulates the Ca-channel current in guinea pig ventricular myocytes.
The effect of intracellular perfusion with cyclic GMP (cGMP) on Ca current (Ica) was investigated in Cs-loaded isolated cells from guinea pig ventricle using the whole-cell patch-clamp technique and a perfused patch pipette. cGMP (5 microM) strongly reduced Ica which had been elevated by intracellular perfusion with 50 microM of either cyclic AMP (cAMP) or its hydrolysis-resistant analog 8-Bromo-cAMP. In addition, cGMP prevented the stimulation of Ica by IBMX, a phosphodiesterase inhibitor. The membrane permeant cGMP analog 8-Bromo-cGMP (100 microM), when applied outside the cell, also antagonized the stimulatory effect of IBMX on Ica. It is concluded that cGMP inhibits Ica in guinea pig ventricular cells by a mechanism different from the activation of a cGMP-stimulated phosphodiesterase recently found in frog ventricular cells.
Levi
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RC
Dipartimento di Biologia Animale, Università di Torino, Italy.
Alloatti
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G
Fischmeister
R
R
D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism*; D004594:Electrophysiology; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000378:metabolism*; D010477:Perfusion; D013997:Time Factors
D015220:Calcium Channels; D000242:Cyclic AMP; D006152:Cyclic GMP