Fig. 2. Absence of apparent Ca²⁺ diffusion between connected rat hepatocytes. Hepatocyte doublets were injected with fura2 and heparin (10 mg/ml in the pipette) as described in methods section. After injection, perfusion (for the time shown by the horizontal bars) of high concentration of noradrenaline (Nor; 10 µM, A) or vasopressin (Vp; 10 nM, B), induced a rapid and strong increase in [Ca²⁺]_i in the noninjected cell only. Although this [Ca²⁺]_i increase was maintained for more than 3 minutes in the responding cell, no diffusion of Ca²⁺ was observed in the connected cell injected with heparin. These results are representative of those obtained using 10 doublets in four independent experiments.