title: Metofenazate as a more selective calmodulin inhibitor than trifluoperazine.
abstract: The interaction of several phenothiazines, benzodiazepines, butyrophenones, polycyclic neuroleptics and tricyclic antidepressants with calmodulin and troponin C was investigated using the fluorescent dye 3,3'-dipropylthiocarbocyanine iodide. In the presence of Ca2+, trifluoperazine (2-trifluoromethyl-10-[3-(1-methylpiperazinyl-4)propyl]-phenothiaz ine dihydrochloride, TFP), which is commonly used as a selective calmodulin inhibitor, half maximally increased the fluorescence of the complex formed of the fluorescent dye with calmodulin at a concentration of 4 mumol/l, and with troponin C at 24 mumol/l. TFP completely inhibited the calmodulin dependent stimulation of cyclic nucleotide phosphodiesterase with a Ki of 4 mumol/l and decreased the maximum Ca2+ dependent troponin C mediated activation of actomyosin ATPase by 35% at a concentration of 100 mumol/l. Metofenazate (3,4,5-trimethoxybenzoate-2-chlor-10-(3-[(beta-oxyethyl) piperazinyl-4]-propyl)phenothiazine diethanesulfonate, methophenazine, MP) produced half maximal fluorescence enhancement of the calmodulin dye complex at a concentration of 6 mumol/l and did not influence the fluorescence of the troponin C dye complex at concentrations of up to 1000 mumol/l. MP also completely inhibited the calmodulin dependent stimulation of phosphodiesterase with a Ki of 7 mumol/l but it had not effect on maximum Ca2+ stimulation of actomyosin ATPase. MP increased the Ca2+ sensitivity of skinned cardiac muscle with an about 10fold lower potency than TFP. In view of these results, we propose MP as a useful tool for distinction between processes mediated by either calmodulin or troponin C.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology*; D002069:Butaclamol / Q000494:pharmacology; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D054677:Cyclic Nucleotide Phosphodiesterases, Type 1; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism; D010640:Phenothiazines / Q000494:pharmacology*; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D013552:Swine; D014268:Trifluoperazine / Q000494:pharmacology*; D014336:Troponin / Q000378:metabolism
chemical_list: D014150:Antipsychotic Agents; D002147:Calmodulin; D010640:Phenothiazines; D014336:Troponin; D014268:Trifluoperazine; C008520:metofenazate; D000205:Actomyosin; D002069:Butaclamol; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054677:Cyclic Nucleotide Phosphodiesterases, Type 1; D000251:Adenosine Triphosphatases