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Due to a printing error, Figure 9 was not printed in its entirety. The corrected figure appears below.

FIGURE 9. Calcium clearance calculated from a kinetic model that includes rate equations for PMCA, NCX, MCU, and Ca²⁺ leak. The assumed resting conditions include a resting membrane potential of -43 mV and a set point for [Na⁺] _i of 16 mM. The equations are in the APPENDIX. (A) Dependence of flux rates on [Ca²⁺]_i for each transport mechanism. Calculations assume resting levels of [Na⁺]_i, control Na7.4 extracellular medium, and a normal resting potential. Rates would be different if any of these conditions are changed. These fluxes represent the number of micromoles of Ca²⁺ transported per second from a liter of cell water (2.3 x 10¹³ sperm). The rate of change of free [Ca²⁺]_i (Table I) would be given by the sum of these values (total) divided by the binding ratio for Ca²⁺. The symbols are values estimated in Table I from our experiments (filled squares, total flux; open triangle, PMCA flux; open circles, NCX flux). (B) Calculated time courses of intracellular free [Ca²⁺] before, during, and after a simulated 10-s alkaline K⁺ depolarization. To mimic the test conditions shown in Figs. 2–7, recovery parameters were changed as follows: the maximum velocity of the PMCA was reduced to 21% (for Na8.6), or [Na⁺]_o was set to zero (for Li7.4), or the MCU flux was turned off (for CCCP), or combinations of these changes were used. (C) The same calculation as in part B but with the velocity of the NCX increased threefold during each period in a Na⁺-free, Li⁺ solution to mimic possible recovery from Na⁺-induced inactivation of the NCX.

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This Article PDF (Full Text) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JGP Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Search for Related Content Social Bookmarking                      What's this?