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The effects of increasing cell length on auxotonic contractions; membrane potential and intracellular calcium transients in single guinea‐pig ventricular myocytes
Author(s) -
White E,
Le Guennec JY,
Nigretto JM,
Gannier F,
Argibay JA,
Garnier D
Publication year - 1993
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.1993.sp003671
Subject(s) - intracellular , biophysics , calcium , sarcomere , myocyte , membrane potential , calcium in biology , chemistry , contraction (grammar) , electrophysiology , cardiac muscle , resting potential , medicine , endocrinology , biology , biochemistry , organic chemistry
Until recently the investigation of length‐dependent effects in cardiac muscle was restricted to multicellular preparations. We describe our experimental set‐up which for the first time, in single cardiac myocytes, permits the effects of changes in cell length on auxotonic contractions (measured by carbon fibre transducers) to be simultaneously recorded with the effects on membrane potential and/or changes in intracellular calcium concentration (using indo‐1 AM, acetoxylmethyl form). Consistent with previous findings (in experiments at 20‐25 degrees C and 0.25 Hz) we report that following a stretch there was an increase in passive tension and contraction. A stretch which increased sarcomere length by approximately 3% had no significant effect on resting membrane potential or action potential amplitude. There was, however, a significant decrease in the action potential duration (P < 0.01, n = 8). No significant change in the amplitude of the intracellular calcium transient was seen following a stretch but a reduction in its duration was observed (P < 0.025, n = 11). Our observations on intracellular calcium transients are consistent with the hypothesis that, in mechanically loaded preparations, their time course is more dependent on changes in tension than changes in length.