title: Validation of formamide as a detubulation agent in isolated rat cardiac cells.
abstract: Kawai M, Hussain M, and Orchard CH. Am J Heart Circ Physiol 277: H603-H609, 1999 developed a technique to detubulate rat ventricular myocytes using formamide and showed that detubulation results in a decrease in cell capacitance, Ca(2+) current density, and Ca(2+) transient amplitude. We have investigated the mechanism of this detubulation and possible direct effects of formamide. Staining ventricular cells with di-8-ANEPPS showed that the t tubule membranes remain inside the cell after detubulation; trapping of FITC-labeled dextran within the t tubules showed that detubulation occurs during formamide washout and that the t tubules appear to reseal within the cell. Detubulation had no effect on the microtubule network but resulted in loss of synchronous Ca(2+) release on electrical stimulation. In contrast, formamide treatment of atrial cells did not significantly change cell capacitance, Ca(2+) current amplitude, action potential configuration, the Ca(2+) transient or the response of the Ca(2+) transient to isoprenaline. We conclude that formamide washout induces detubulation of single rat ventricular myocytes, leaving the t tubules within the cell, but without direct effects on cell proteins that might alter cell function.
authors.affiliation: School of Biomedical Sciences, University of Leeds, United Kingdom.
authors.forename: Fabien
authors.initials: F
authors.lastname: Brette
authors.forename: Kimiaki
authors.initials: K
authors.lastname: Komukai
authors.forename: Clive H
authors.initials: CH
authors.lastname: Orchard
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002316:Cardiotonic Agents / Q000494:pharmacology; D004594:Electrophysiology; D005456:Fluorescent Dyes; D005559:Formamides / Q000494:pharmacology*; D006325:Heart Atria / Q000166:cytology; D007545:Isoproterenol / Q000494:pharmacology; D008870:Microtubules / Q000187:drug effects; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000502:physiology; D009206:Myocardium / Q000166:cytology*; D011726:Pyridinium Compounds; D051381:Rats; D012508:Sarcolemma / Q000187:drug effects*
chemical_list: C089669:1-(3-sulfonatopropyl)-4-(beta-(2-(di-n-octylamino)-6-naphthyl)vinyl)pyridinium betaine; D002316:Cardiotonic Agents; D005456:Fluorescent Dyes; D005559:Formamides; D011726:Pyridinium Compounds; C031066:formamide; D007545:Isoproterenol; D002118:Calcium