title: Changes in [Ca2+]i, [Na+]i and Ca2+ current in isolated rat ventricular myocytes following an increase in cell length.
abstract: Isolated rat ventricular myocytes were stretched using carbon fibres to investigate the mechanisms underlying the increase in contraction following stretch. 2. [Ca2+]i and [Na+]i were monitored using the fluorescent indicators fura-2 and sodium-binding benzofuran isophthalate, respectively. The L-type Ca2+ current was recorded simultaneously with contraction using the perforated patch-clamp technique. 3. Mechanical stretch caused an immediate increase in contraction, followed by a slow increase. Contraction was prolonged immediately after the stretch, but did not change during the slow phase. 4. The Ca2+ transient did not change immediately after the stretch. The slow increase in contraction was accompanied by an increase in the amplitude of the Ca2+ transient. However, diastolic [Ca2+]i did not change significantly following stretch. 5. [Na+]i did not change significantly either immediately, or during the slow increase in contraction, after the stretch. 6. The L-type Ca2+ current was not significantly altered either by mechanical loading of the cell with carbon fibres or by stretching the cell. 7. These results suggest that: (1) the rapid increase in contraction following a stretch is due to an increase in myofilament Ca2+ sensitivity rather than to changes in the L-type Ca2+ current or [Na+]i; and (2) a slow increase in the Ca2+ transient underlies the slow increase in contraction in isolated myocytes, but is not caused by either an increase in diastolic [Ca2+]i or a change in [Na+]i (and hence Ca2+ influx via Na(+)-Ca2+ exchange) or a change in myofilament Ca2+ sensitivity.
authors.affiliation: Department of Physiology, University of Leeds, UK.
authors.forename: K
authors.initials: K
authors.lastname: Hongo
authors.forename: E
authors.initials: E
authors.lastname: White
authors.forename: J Y
authors.initials: JY
authors.lastname: Le Guennec
authors.forename: C H
authors.initials: CH
authors.lastname: Orchard
mesh_terms: D000818:Animals; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D048429:Cell Size / Q000502:physiology; D004988:Ethers, Cyclic; D005456:Fluorescent Dyes; D016257:Fura-2; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D066298:In Vitro Techniques; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure*; D018408:Patch-Clamp Techniques; D051381:Rats; D012964:Sodium / Q000378:metabolism*
chemical_list: D001572:Benzofurans; D015220:Calcium Channels; D004988:Ethers, Cyclic; D005456:Fluorescent Dyes; C061665:sodium-binding benzofuran isophthalate; D012964:Sodium; D002118:Calcium; D016257:Fura-2