Genistein directly induces cardiac CFTR chloride current by a tyrosine kinase-independent and protein kinase A-independent pathway in guinea pig ventricular myocytes.
With one-suction electrode voltage-clamp technique, we demonstrated that genistein, a tyrosine kinase (TK) inhibitor, could directly activate cystic fibrosis transmembrane regulator (CFTR) chloride current in guinea pig ventricular myocytes. The activation showed concentration-dependent effect with the estimated IC50 of 39.7 microM. Tyrphostin 51, another TK inhibitor, had no effect, suggesting that genistein's effect might be unrelated to TK inhibition. After the chloride current had been activated by the maximally elevated intracellular cAMP content by saturating concentration of isoproterenol, forskolin and IBMX, genistein could further enhance the current. Pre-treatment with saturating concentration of a specific protein kinase A (PKA) inhibitor, H-89, or other protein kinase inhibitors H-8 and H-9 in the perfusate or intracellularly could not prevent the activation of the current by genistein, suggesting a PKA-independent activity. Furthermore, saturating concentration of calyculin A, a specific inhibitor of phosphotase 1 and 2A, in the perfusate or intracellularly could not block genistein's action. It is possible that genistein opens the channels directly or inhibits the dephosphorylation process of CFTR, which is not sensitive calyculin A.
Chiang
C E
CE
Division of Cardiology, Veterans General Hospital-Taipei and National Yang-Ming University School of Medicine, Taiwan, Republic of China. cechiang@vghtpe.gov.tw
Chen
S A
SA
Chang
M S
MS
Lin
C I
CI
Luk
H N
HN
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D019833:Genistein; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000187:drug effects; D007529:Isoflavones / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D008387:Marine Toxins; D009206:Myocardium / Q000378:metabolism*; D010080:Oxazoles / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013449:Sulfonamides
D000318:Adrenergic beta-Agonists; D018118:Chloride Channels; D002712:Chlorides; D004791:Enzyme Inhibitors; D007529:Isoflavones; D007546:Isoquinolines; D008387:Marine Toxins; D010080:Oxazoles; D013449:Sulfonamides; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; C004742:daidzein; C059041:calyculin A; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide