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. 2021 Sep 28;9:733653. doi: 10.3389/fcell.2021.733653

FIGURE 6.

FIGURE 6

PKA inhibitor KT5720 impairs the effect of HCO3– on depolarization-evoked Ca2+ responses in ejaculated human sperm. (A–D) Representative traces of [Ca2+]i responses to 50 mM KCl at (A,B) pH 6.8 and (C,D) pH 8.0 in ejaculated human sperm in non-capacitating conditions in (A,C) control and (B,D) after pre-incubation with KT5720. (E) Linear fit of the averaged normalized fluorescence in the first 20 s after KCl addition. (F) Graph of slope values of the best-fit regression line for each condition. Mean values at pH 6.8 were as follows: control, 1.80 ± 0.82 amplitude units * s–1 (26 samples, 1836 sperm); and KT5720 pre-incubation, 0.426 ± 0.277 amplitude units *s–1 (6 samples, 624 sperm). Mean values at pH 8.0 were as follows: control, 1.73 ± 0.594 amplitude units * s–1 (26 samples, 3036 sperm); and KT5720 pre-incubation, 0.678 ± 0.162 amplitude units *s–1 (5 samples, 974 sperm). (G) Graph of the percentage of responsive sperm. Mean values at pH 6.8 were as follows: control, 66.94% ± 24.30 (26 samples, 1836 sperm); and KT5720 pre-incubation, 31.57% ± 10.87 (6 samples, 624 sperm). Mean values at pH 8.6 were as follows: control, 77.04% ± 18.67 (26 samples, 3036 sperm); and KT5720 pre-incubation, 36.90% ± - 15.33 (6 samples, 974 sperm). **P < 0.010, ***P < 0.001 by independent t-test. Error bars indicate standard deviation. Iono = 5 μM Ionomycin + 2 mM Ca2+.