Fig. 7. Ester loading of cAMP mimics the actions of bicarbonate. Sperm were incubated 30 minutes with 60 µM of cAMP-AM. Aliquots of these loaded sperm (cAMP-AM) were transferred to a bath containing medium Na7.4 that also contained 60 µM of cAMP-AM (A) or Na7.4 alone (B-D) and examined immediately. Other samples of untreated sperm (stored in medium Na7.4) were transferred to a bath containing medium Na7.4 alone (none) or with 15 mM NaHCO₃ (15 BC). (A) Depolarization-evoked [Ca²⁺]_i responses were monitored in three independent experiments as in Fig. 1, except that cells were perfused continuously only during application of medium K8.6. Mean values were 17±4 (none; n=17), 41±6 (cAMP-AM; n=16), and 55±8 (15 BC; n=19) nM second^-1. Waveform analysis was performed as in Fig. 3 (but without perfusion) to provide flagellar beat frequency (B) and beat amplitude (C), and as in Fig. 5 (but without perfusion) to provide the time-averaged tangent angle (D). Mean values (n=24 for each treatment group; eight cells per group in three independent experiments) were 2.6±01, 6.7±0.3 and 8.3±0.4 Hz; 24.8±1.0, 20.5±1.2 and 20.1±0.7 µm.