MECHANICAL MEASUREMENTS FROM ISOLATED CARDIAC MYOCYTES USING A PIPETTE ATTACHMENT SYSTEM

Single rat left ventricular myocytes were attached at both ends using a newly described double-barreled micropipette technique. This attachm ent procedure enabled the measurement of the active and passive mechan ical properties of chemically shinned cells that showed little structu ral deformation. The force and oscillatory stiffness (100 Hz) of the c ells were measured with a high signal-to-noise ratio, and the sarcomer e length throughout the entire cell was monitored using image analysis . The passive properties were investigated from the resting sarcomere length to >3 Hm Analysis of the sarcomere behavior indicated a high le vel of homogeneity throughout the cell. The attachment method supporte d the full activation of the cells by increased free Ca2+ (pCa 4.5), w hich produced 22.3 mN/mm (mean sarcomere length 2.11 mu m). A force/pC a relationship was determined, which, when fitted according to the Hil l equation, gave parameters of n(H) = 2.62 and pCa(50) = 5.58. The des cribed techniques allow the accurate study of the mechanical propertie s of single myocytes with increased fidelity and reliability over the preexisting methods.