Relationship between motility and the transport and binding of divalent cations to the plasma membrane of human spermatozoa.

Measurements of fluorescence changes of the divalent cation probe chlortetracycline, which accumulates in the plasma membrane of human spermatozoa, and measurements of radioactive calcium uptake indicate that the plasma membrane of human spermatozoa is impermeable to calcium. Moreover, permeability to exogenous calcium is not changed when sperm motility is stimulated by agents which increase intracellular levels of adenosine 3':5'-monophosphate (cyclic AMP). Evidence is presented, however, which suggests that energy-dependent divalent cation binding to the plasma membrane is lowered when motility is increased by cyclic AMP phosphodiesterase inhibitors.