title: Testosterone inhibits the prostaglandin F2alpha-mediated increase in intracellular calcium in A7r5 aortic smooth muscle cells: evidence of an antagonistic action upon store-operated calcium channels.
abstract: Testosterone-induced vasodilatation is proposed to contribute to the beneficial effects associated with testosterone replacement therapy in men with cardiovascular disease, and is postulated to occur via either direct calcium channel blockade, or through potassium channel activation via increased production of cyclic nucleotides. We utilised flow cytometry to investigate whether testosterone inhibits the increase in cellular fluorescence induced by prostaglandin F(2alpha) in A7r5 smooth muscle cells loaded with the calcium fluorescent probe indo-1-AM, and to study the cellular mechanisms involved. Two-minute incubation with testosterone (1 microM) significantly inhibited the change in cellular fluorescence in response to prostaglandin F(2alpha) (10 microM) (3.6+/-0.6 vs 7.6+/-1.0 arbitrary units, P=0.001). The change in cellular fluorescence in response to prostaglandin F(2alpha) (10 microM) was also significantly attenuated in the absence of extracellular calcium (3.6+/-0.3 vs 15.6+/-0.7 arbitrary units, P=0.0000002), and by a 2-min incubation with the store-operated calcium channel blocker SK&F 96365 (50 microM) (4.7+/-0.8 vs 8.1+/-0.4 arbitrary units, P=0.003). The response was insensitive to similar incubation with the voltage-operated calcium channel blockers verapamil (10 microM) (12.6+/-1.2 vs 11.9+/-0.2 arbitrary units, P=0.7) or nifedipine (10 microM) (13.9+/-1.3 vs 13.3+/-0.5 arbitrary units, P=0.7). Forskolin (1 microM) and sodium nitroprusside (100 microM) significantly increased the cellular concentration of cyclic adenosine monophosphate and cyclic guanosine monophosphate respectively, but testosterone (100 nM-100 microM) had no effect. These data indicate that the increase in intracellular calcium in response to prostaglandin F(2alpha) occurs primarily via extracellular calcium entry through store-operated calcium channels. Testosterone inhibits the response, suggesting an antagonistic action upon these channels.
authors.affiliation: Academic Unit of Endocrinology, Division of Genomic Medicine, The University of Sheffield, Sheffield, UK. R.D.Jones@sheffield.ac.uk
authors.forename: R D
authors.initials: RD
authors.lastname: Jones
authors.forename: L N
authors.initials: LN
authors.lastname: Ruban
authors.forename: I E
authors.initials: IE
authors.lastname: Morton
authors.forename: S A
authors.initials: SA
authors.lastname: Roberts
authors.forename: K M
authors.initials: KM
authors.lastname: English
authors.forename: K S
authors.initials: KS
authors.lastname: Channer
authors.forename: T H
authors.initials: TH
authors.lastname: Jones
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002460:Cell Line; D002614:Chelating Agents; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D015224:Dideoxynucleosides; D015237:Dinoprost / Q000494:pharmacology*; D005434:Flow Cytometry; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles; D007424:Intracellular Fluid / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D013739:Testosterone / Q000494:pharmacology*; D014700:Verapamil / Q000494:pharmacology
chemical_list: C095793:6-chloro-2',3'-dideoxyguanosine; D002121:Calcium Channel Blockers; D002614:Chelating Agents; D015224:Dideoxynucleosides; D007093:Imidazoles; D007211:Indoles; D020030:Nitric Oxide Donors; C059587:Indo-1 pentaacetoxymethyl ester; D009599:Nitroprusside; D005576:Colforsin; D013739:Testosterone; D015237:Dinoprost; D014700:Verapamil; D000242:Cyclic AMP; D006152:Cyclic GMP; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D009543:Nifedipine; D002118:Calcium