Fig. 2.

ATP-induced increases in intracellular Ca²⁺ concentration ([Ca²⁺]_i) in Ca²⁺-buffered developing cardiomyocytes. A: normalized fluorescence images from a neonatal cardiomyocyte show low noise before activation (control; F/F_o ≅ 1) and subsarcolemmal increases in [Ca²⁺]_i following application of 100 μM ATP. B: average cellular Ca²⁺ transients (ΔF/F_o) in neonatal (Neo; solid bars; 1 to 2 days old) and juvenile (Juv; hatched bars; 8–10 days old) cardiomyocytes in response to 100 μM ATP (left) or 100 nM endothelin-1 (ET-1; right). Voltage-clamped cells are same color scale as Fig. 1.