Premium
Cytochrome P450: a novel system modulating Ca 2+ channels and contraction in mammalian heart cells
Author(s) -
Xiao YongFu,
Huang Lin,
Morgan James P.
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.777bp.x
Subject(s) - clotrimazole , econazole , chemistry , intracellular , pharmacology , isoprenaline , endocrinology , medicine , miconazole , biochemistry , biology , antifungal , stimulation , microbiology and biotechnology
1 Cytochrome P450 (P450) is a ubiquitous enzyme system that catalyses oxidative reactions of numerous endogenous and exogenous compounds. The modulatory effects of P450 on the L‐type Ca 2+ current ( I Ca ), intracellular free Ca 2+ signals and cell shortening were assessed in adult rat single ventricular myocytes. 2 Bath administration of the imidazole antimycotics, clotrimazole, econazole and miconazole, which are potent P450 inhibitors, significantly suppressed cardiac I Ca . While the Ca 2+ channel antagonist nifedipine blocked I Ca within 30 s, clotrimazole‐induced suppression of I Ca required 5.1 ± 0.4 min ( n = 14 ) to reach a steady low level. The suppression of I Ca was dose dependent and recovered after washout of clotrimazole. Intracellular dialysis with the P450 antibody anti‐rat CYP1A2 also significantly reduced cardiac I Ca . 3 Additional administration of the β‐adrenergic agonist isoprenaline (1 μM) or the membrane‐permeable 8‐bromo‐cAMP (2 mM) completely reversed the suppressant effects of clotrimazole and NaCN on I Ca . In addition, intracellular dialysis with 2 mM cAMP abolished the P450 inhibitor‐induced suppression of I Ca . Phosphorylation of the channel with hydrolysis‐resistant ATPγS prevented the suppressant effect of clotrimazole on I Ca . Furthermore, dephosphorylation of the Ca 2+ channel with intracellular dialysis with phosphatase types I and II reduced I Ca by 85 ± 3 % and abolished clotrimazole‐induced suppression of I Ca . 4 Extracellular administration of the phospholipase A 2 inhibitors mepacrine and 4‐bromophenacyl bromide significantly suppressed I Ca . 5 Clotrimazole, econazole, miconazole and CN − also significantly inhibited intracellular free Ca 2+ signals and cell shortening in rat single ventricular myocytes. 6 Intracellular cAMP content was significantly reduced in isolated ventricular myocytes incubated with clotrimazole or CN − . Extracellular administration of 11, 12‐epoxyeicosatrienoic acid, one of the P450‐mediated metabolites of arachidonic acid, enhanced I Ca and intracellular cAMP content. The epoxyeicosatrienoic acid also restored the amplitude of the reduced I Ca in P450 antibody‐dialysed myocytes. 7 The present data suggest that cytochrome P450 modulates cardiac I Ca and cell contraction, and the modulation may result from changes in intracellular levels of cAMP by P450‐ mediated metabolites of arachidonic acid.