Figure 4.
![Figure 4. Ca2+ spark frequency is represented as a surface and is shown as a function of both [Mg2+]free and [ATP]free. The bivariate correlation coefficients obtained from a multivariate regression model for the Ca2+ spark frequency dependence on [Mg2+]free was −0.425 (P = 0.005) and on [ATP]free was +0.116 (P = 0.47). For details of the multivariate analysis see Materials and methods and Table S1.](https://cdn.rupress.org/rup/content_public/journal/jgp/132/6/10.1085_jgp.200810119/6/jgp_200810119_rgb_fig4.jpeg?Expires=1773655145&Signature=nDIuymkfZBaaXaSMyxv43jDRNEYCQXYhCkcMbb6iZlUyDtOFIEFhw0uqYlAqpM~lYJMPQXg8gCVqElnu6X-My-GcT8Srf0Xsu78Inx33i0vcI0zzcW1Ms2u2Vancz2bDR2MeZfVYIWolyqgNUymrzsnrDNyZ8VAOwLD1o-V1g2VwWJL4wjjGzIwfKKRYyqJazp1pjrs7JigZWt5vaL9CKG8INEP5-5ikzOMj2lXrYJ9wvj1P4JlGwdu5rW2LBXSKEg5ArZ~ALxpSeHRTih92d4~5ISQwgR~GMMXRFIV59Z3PNLclH3oSvJBbiaA13Lfzvo5MzUVIWZbHeEG5vaQGrw__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Ca2+ spark frequency is represented as a surface and is shown as a function of both [Mg2+]free and [ATP]free. The bivariate correlation coefficients obtained from a multivariate regression model for the Ca2+ spark frequency dependence on [Mg2+]free was −0.425 (P = 0.005) and on [ATP]free was +0.116 (P = 0.47). For details of the multivariate analysis see Materials and methods and Table S1.
