FIGURE 4.

CAII and CAIV activity in sperm and expression levels in the male reproductive tract of WT, CAII^−/−, and CAIV^−/− mice. A, CA activity was measured with mass spectrometry. In comparison with WT sperm, the deletion of CAII or CAIV leads to a reduction in activity of 32% and 65%, respectively. CA activity in CAII^−/− CAIV^−/− mice is 0.7 units/ml (± 0.02), which equals a reduction of 86.9%. Data are mean ± S.E. of six or more measurements from three independent experiments. The asterisks refer to the values of the bar for WT. *, p ≤ 0.05; **, p ≤ 0.01; ***, p ≤ 0.001. B, analysis of the single-sperm beat frequency response to 15 mm HCO₃⁻. CAII^−/− and CAIV^−/− sperm display a delayed and reduced acceleration of beat frequency. Data are mean ± S.E. of ≥40 single sperm. C, expression of CAII and CAIV mRNA in WT tissue detected by qRT-PCR. D and E, in relation to WT tissue, CAIV is overexpressed in the caput, corpus, and cauda epididymidis (epi.) of CAII^−/− mice (D), whereas CAII expression is highly increased in the cauda epididymidis and vas deferens (vas def.) of CAIV^−/− animals (E) (n = 3).