Stretch-induced increase of resting intracellular calcium concentration in single guinea-pig ventricular myocytes.

Single guinea-pig ventricular myocytes were loaded with the fluorescent Ca2+ indicator Indo-1 AM and stretched by carbon fibres. Stretching increased resting tension. Sarcomere lengths were increased by 2-18%. It was observed that a stretch increased resting [Ca2+]i in seven out of eight cells. The change in [Ca2+]i increased with the size of the stretch and returned to pre-stretch levels on return to resting cell length. These observations suggest a means by which changes in resting muscle length can modify the contractile state of cardiac muscle.