title: Molecular requirements for L-type Ca2+ channel blockade by testosterone.
abstract: Despite being generally perceived as detrimental to the cardiovascular system, testosterone has marked beneficial vascular effects; most notably it acutely and directly causes vasodilatation. Indeed, men with hypotestosteronaemia can present with myocardial ischemia and angina which can be rapidly alleviated by infusion of testosterone. To date, however, in vitro studies have failed to provide a convincing mechanism to account for this clinically important effect. Here, using whole-cell patch-clamp recordings to measure current flow through recombinant human L-type Ca2+ channel alpha(1C) subunits (Ca(v)1.2), we demonstrate that testosterone inhibits such currents in a concentration-dependent manner. Importantly, this occurs over the physiological range of testosterone concentrations (IC50 34 nM), and is not mimicked by the metabolite 5alpha-androstan-17beta-ol-3-one (DHT), nor by progesterone or estradiol, even at high (10 microM) concentration. L-type Ca2+ channels in the vasculature are also important clinical targets for vasodilatory dihydropyridines. A single point mutation (T1007Y) almost completely abolishes nifedipine sensitivity in our recombinant expression system. Crucially, the same mutation renders the channels insensitive to testosterone. Our data strongly suggest, for the first time, the molecular requirements for testosterone binding to L-type Ca2+ channels, thereby supporting its beneficial role as an endogenous Ca2+ channel antagonist in the treatment of cardiovascular disease.
authors.affiliation: Institute for Cardiovascular Research, School of Medicine, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Jason L
authors.initials: JL
authors.lastname: Scragg
authors.forename: Mark L
authors.initials: ML
authors.lastname: Dallas
authors.forename: Chris
authors.initials: C
authors.lastname: Peers
mesh_terms: D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects* / Q000235:genetics; D002478:Cells, Cultured; D013196:Dihydrotestosterone / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D006801:Humans; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D017354:Point Mutation; D011374:Progesterone / Q000494:pharmacology; D011994:Recombinant Proteins / Q000187:drug effects; D013329:Structure-Activity Relationship; D013739:Testosterone / Q000494:pharmacology*
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; C419385:L-type calcium channel alpha(1C); D011994:Recombinant Proteins; D013196:Dihydrotestosterone; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; D009543:Nifedipine