Figure 5.
Panel A shows a line graph of total released calcium concentration over time. The vertical axis represents calcium concentration in micromolar, and the horizontal axis represents time in milliseconds. Multiple lines indicate measurements at different voltage levels, ranging from minus fifty-seven millivolts to minus seventy-two millivolts. Panel B presents a semilogarithmic plot of the rate of change of calcium concentration, or calcium flux, versus applied voltage. The vertical axis represents flux in micromolar per millisecond on a logarithmic scale, while the horizontal axis represents the applied voltage in millivolts. The data points form a linear trend, indicating an e-fold increase, meaning an increase by a factor of approximately two point seven one eight, in flux for every three point seven three millivolts change in voltage.
Evolution of total released Ca 2+ in a voltage-clamped frog myofiber. (A) Total released Ca2+ vs. time. Ca2+ concentration was measured with Fura-2 and total released was quantified as the increase in total cytoplasmic Ca2+ (Δ[CaT]), mostly bound by EGTA in the experiment. Flux is the rate of change of the records in A (dΔ[CaT]/dt). (B) Semilog plot of flux vs. applied voltage, with a slope corresponding to an e-fold increase every 3.73 mV. Reproduced Fig. 14 in Pape et al. (1995).