title: Large-conductance chloride channels of new-born rat cardiac myocytes are activated by hypotonic media.
abstract: Large-conductance chloride (LC-type Cl-) channel activity was studied in rat ventricular myocyte membrane during development. In contrast with results previously obtained in cultured ventricular myocytes of the new-born rat, we failed to record single-channel activity in freshly isolated myocytes whatever the age of the animal (from 2 days old to adult) and the recording patch configuration used. However, spontaneous single-channel activity of LC-type Cl- channels was recorded in bleb membranes of myocytes of rats younger than 12 days, with a higher frequency in excised inside-out membrane patches than in cell-attached membrane patches. In intact neonatal myocytes, application of hypotonic media (150 mOsm) also initiated the channel activity, after variable delays (25-200 s). The channel could not be activated by suction applied through the pipette and was not observable in cells from rats older than 15 days. The LC-type Cl- channels showed properties similar to those reported in other preparations and previously observed in cardiac cultured cells: they had a large single-channel conductance of 400 pS in symmetrical 150 mM NaCl, showed multiple subconductance states, a relatively high selectivity to Cl- ions over Na+ ions (PCl/PNa = 24.6), were blocked by 10 microM 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid (SITS) and showed voltage-dependent inactivation. They were not activated by 10 microM colchicine or 3 microM cytochalasin D.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000375:Aging / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D002712:Chlorides / Q000378:metabolism*; D003470:Culture Media; D004553:Electric Conductivity; D007038:Hypotonic Solutions / Q000494:pharmacology*; D007473:Ion Channels / Q000502:physiology*; D008566:Membranes / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D051381:Rats
chemical_list: D002712:Chlorides; D003470:Culture Media; D007038:Hypotonic Solutions; D007473:Ion Channels