Mechanical stretch increases intracellular calcium concentration in cultured ventricular cells from neonatal rats

We investigated the effects of mechanical stretch on intracellular calcium concentration ([Ca2+](i)) of cultured neonatal rat ventricular cells using microfluorometry with fura-2. Myocytes were cultured on laminin-coated silicon rubber and stretched by pulling the rubber with a manipulator Myocytes were either mildly stretched (to less than 115% of control length) moderately so (to 115%-125% of control length), or extensively (to over 125% of the control length). ''Quick stretches'' (accomplished within 10s) of moderate to extensive intensities produced a large transient increase of [Ca2+](i) in the early phase of stretch (30s-2 min), followed by a small but sustained increase during the late phase of stretch (5-10 min). The initial transient increase in [Ca2+](i) after the ''quick stretch'' was preserved in the presence of gallopamil (10(-7) M) or ryanodine (10(-5) M), but was absent in Ca2+-free medium or in the presence of gadolinium (10(-7) M). The late or steady state [Ca2+](i) increase was observed in the presence of gadolinium, gallopamil, or ryanodine but was abolished in Ca2+-free medium. A steady-state increase in [Ca2+](i) was also evoked by ''slow stretch'' in which cells were slowly pulled to the final length within 1-2 min. As the presence of external Ca2+ was indispensable, increased trans-sarcolemmal Ca2+ influx appears to be involved in both initial and steady-slate increases in [Ca2+](i). The initial increase in [Ca2+](i) after the ''quick stretch'' can be attributed to the activation of gadolinium-sensitive, stretch-activated channels.