The reaction of CO₂ with H₂O to form bicarbonate (HCO₃⁻) and H⁺ controls sperm motility and fertilization via HCO₃⁻-stimulated cAMP synthesis. A complex network of signaling proteins participates in this reaction. Here, we identify key players that regulate intracellular pH (pH_i) and HCO₃⁻ in human sperm by quantitative mass spectrometry (MS) and kinetic patch-clamp fluorometry. The resting pH_i is set by amiloride-sensitive Na⁺/H⁺ exchange. The sperm-specific putative Na⁺/H⁺ exchanger SLC9C1, unlike its sea urchin homologue, is not gated by voltage or cAMP. Transporters and channels implied in HCO₃⁻ transport are not detected, and may be present at copy numbers < 10 molecules/sperm cell. Instead, HCO₃⁻ is produced by diffusion of CO₂ into cells and readjustment of the CO₂/HCO₃⁻/H⁺ equilibrium. The proton channel H_v1 may serve as a unidirectional valve that blunts the acidification ensuing from HCO₃⁻ synthesis. This work provides a new framework for the study of male infertility.

_{CO 2}与H ₂ O反应形成碳酸氢盐(HCO ₃ ^- )和H ⁺通过HCO ₃ ^-刺激cAMP合成来控制精子活力和受精。信号蛋白的复杂网络参与该反应。在这里，我们通过定量质谱 (MS) 和动态膜片钳荧光测定法确定了调节人类精子细胞内 pH (pH _i ) 和 HCO ₃ ^{−的关键因素。}静息 pH _{i由阿米洛利敏感的 Na} ⁺ /H ⁺交换设定。精子特异性的假定 Na ⁺ /H ⁺交换器 SLC9C1 与其海胆同源物不同，不受电压或 cAMP 门控。_{未检测到 HCO 3} ^-转运中隐含的转运蛋白和通道，并且可能以 < 10 个分子/精子细胞的拷贝数存在。相反，HCO ₃ ^-是通过CO ₂扩散到细胞中并重新调整CO ₂ /HCO ₃ ^- /H ⁺平衡而产生的。质子通道H _v 1 可充当单向阀，其减弱由HCO ₃ ^-合成引起的酸化。这项工作为男性不育症的研究提供了一个新的框架。