Abstract
The aim of this study was to determine the effects of the antiestrogen agent clomiphene on cardiac anionic and cationic sarcolemmal ion channels. Whole-cell recordings were made from rat and guinea pig ventricular myocytes. Clomiphene inhibited the volume-regulated chloride current [ICl,vol, activated by cell swelling after hypotonic shock (∼145 mOsM)] with an IC50 value of ∼9.4 μM. In contrast, at concentrations up to 100 μM, clomiphene failed to inhibit both the chloride current activated by cyclic AMP (ICl,cAMP) and the anionic background current (IAB). At 10 μM, clomiphene blocked the voltage-gated fast sodium current and the L-type calcium current (ICa,L) in both species. The voltage-independent fractional block ofICa,L induced by clomiphene (10 μM) was ∼82%, this concentration also inhibited the inwardly rectifying K+ current with a fractional current block of ∼26% at −90 mV. Fractional block of outward current at +70 mV in rat was ∼25%, implying that delayed rectifying K+ channels were also affected by clomiphene. We conclude that clomiphene shows selectivity for ICl,vol overICl,cAMP and IABand therefore represents a useful tool for studying chloride conductances in isolated ventricular myocytes with interfering currents blocked. However, due to its effects on cation conductances it would be of little value in this regard for other types of in vitro or in vivo experiments.
Footnotes
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↵1 Current address: Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK.
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↵2 Current address: Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, 5501 Hopkins Bayview Circle, Baltimore, MD 21224.
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J.J.B. was funded through a University of Bristol Scholarship and through the ORS Award Scheme 2000 (United Kingdom Scholarships for International Research Students). J.C.H. was supported by a fellowship from the Wellcome Trust. This work was funded by the Medical Research Council and Oxford Molecular PLC.
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DOI: 10.1124/jpet.102.038901
- Abbreviations:
- CLM
- clomiphene
- VRAC
- volume-regulated anion channel
- CPAE
- cultured pulmonary artery endothelial cell
- ICl,vol
- volume-regulated chloride current
- INa
- voltage-gated sodium current
- ISO
- isoosmotic
- HTS
- hyposmotic solution
- FSK
- forskolin
- ICl,cAMP
- cAMP-activated chloride current
- IK1
- inward rectifying potassium current
- I-V
- current-voltage
- IAB
- anionic background current
- NMDG
- N-methyl-d-glucamine
- ICa,L
- L-type calcium current
- DIDS
- diisothiocyanostilbene-2,2′-disulfonic acid
- ECl
- reversal potential for chloride
- IKv
- voltage-gated potassium current
- TTX
- tetrodotoxin
- Received May 10, 2002.
- Accepted June 21, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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