title: Carbonic anhydrase inhibitors ameliorate the symptoms of hypokalaemic periodic paralysis in rats by opening the muscular Ca2+-activated-K+ channels.
abstract: Carbonic-anhydrase inhibitors are effective in channelopathies possibly by opening the Ca2+-activated-K+ channels. However, the in vivo effects of these drugs in K+-deficient rats, the animal model of familial hypokalaemic periodic paralysis(hypokalaemic-PP), are currently unknown. Measures of insulin-responses, serum electrolytes levels and patch-clamp experiments were therefore performed in K+ -deficient rats treated in vivo with dichlorphenamide (DCP), ethoxzolamide (ETX), hydrochlorthiazide (HCT), methazolamide (MTZ), bendroflumethiazide (BFT) and acetazolamide (ACTZ). Ten days treatments of K+-deficient rats with DCP, BFT, ETX and ACTZ (5.6 mg/kg per day) restored the serum [K+] to control values and prevented the insulin-induced paralysis. In ex vivo experiments, the carbonic-anhydrase inhibitors enhanced the activity of Ca2+-activated-K+ channels with the order of efficacy: ACTZ>BFT>ETX>DCP. In contrast, HCT and MTZ failed to stimulate the Ca2+-activated-K+ channels and to prevent the hypokalaemia and paralysis. At the concentration of 1mg/kg per day, all these drugs failed to ameliorate the hypokalaemic-PP symptoms. The activation of Ca2+-activated-K+ channel in addition to the mild diuretic effect explained the efficacy of ACTZ and DCP in K+ -deficient rats and in familial hypokalaemic-PP.
authors.affiliation: Unit of Pharmacology, Department of Pharmacobiology, Faculty of Pharmacy, University of Bari, via Orabona no. 4,70126 Bari, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Tricarico
authors.forename: Antonietta
authors.initials: A
authors.lastname: Mele
authors.forename: Diana
authors.initials: D
authors.lastname: Conte Camerino
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002257:Carbonic Anhydrase Inhibitors / Q000627:therapeutic use*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D020514:Hypokalemic Periodic Paralysis / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009132:Muscles / Q000187:drug effects* / Q000503:physiopathology; D018408:Patch-Clamp Techniques / Q000379:methods; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects* / Q000502:physiology; D011191:Potassium Deficiency / Q000150:complications; D051381:Rats; D017208:Rats, Wistar; D013053:Spectrophotometry / Q000379:methods
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D024681:Potassium Channels, Calcium-Activated; D000255:Adenosine Triphosphate; D002118:Calcium