Figure 1. ATP increases cytosolic free calcium concentration in isolated fura-2-loaded Necturus PCT.

Fura-2 fluorescence was monitored and converted to R_340/380 values as described in Methods. A a PCT was continuously superfused with Ringer medium and exposed to 100 μmol l⁻¹ ATP for the period indicated by the horizontal bar. B effects of repeated exposures to ATP on [Ca²⁺]_i of Necturus PCT. A fura-2-loaded PCT bathed in Ringer medium was exposed to 100 μmol l⁻¹ ATP for the periods indicated by the horizontal bars. The trace shown is representative of 4 similar experiments.