Fig. 7. GalT I-null sperm exhibit constitutively increased levels of cAMP during capacitation in HCO₃^– -containing or HCO₃^– -free media. Wild-type (gt +/+) and GalT I-null (gt –/–) were capacitated for varying periods of time in HCO₃^– -containing or HCO₃^– -free media. The cAMP in 1x10⁶ sperm was extracted with ice-cold ethanol and detected by enzyme immunoassay. Each bar represents the mean±s.e.m.; n=4 experiments. For a single experiment, the value for each data point represents the average of two determinations (for a total of eight assays).