IN-SITU ELECTROCHEMISTRY OF RU(NH3)(6)(3-HEART() IN A PERFUSED RAT)

Simple two-electrode potential sweep and potential step electrochemica l measurements are reported in a perfused living rat heart prepared us ing a modified in situ Langendorff preparation. Cyclic voltammetry of Ru(NH3)(6)(3+) at Pt electrodes is performed in vivo after retrograde aortic perfusion of Ca2+- and albumin-free, oxygenated Krebs buffer co ntaining Ru(NH3)(6)(3+) to assess uniformity of perfusion. Four types of voltammetric response are observed depending on the placement of th e working electrode. These types are distinguished on the basis of the relative contributions of diffusive and hydrodynamic mass transport a s manifest in the shapes of the current-potential curves. Chronoampero metric measurement of double layer charging was used to estimate extra cellular tissue resistance. These chronoamperometric experiments are p erformed in buffer solutions by small potential steps around a set pot ential of non-Faradaic activity. Tissue resistance was estimated to be ca. 598 +/- 138 Omega from the chronoamperometric data. The electroch emical responses observed from both measurements exhibit good reproduc ibility between individual heart preparations.