No abstract

Freshly ejaculated, noncapacitated boar sperm bind rapidly and in large numbers to pig egg zona pellucida in vitro. In the present study, the number of sperm bound decreased sharply when sperm motility was lowered by energy poisons or by reducing the temperature. Highly motile sperm from humans, guinea pigs, and rats, added at concentrations ten times higher than control sperm, did not bind to the porcine zona. At the same high concentration, a small number of hamster and bull sperm bound to the zona. Binding of boar sperm to the zona pellucida was blocked almost completely by diluted whole antiserum to sperm plasma membranes and by univalent (Fab) antibody to these membranes. When antibody to sperm plasma membrane was first absorbed with plasma membrane vesicles, sperm binding was not inhibited. These results provide direct evidence for the existence of sperm plasma membrane receptors for the zona pellucida of the pig.

No abstract

Radioactive calcium uptake by suspensions of washed boar and human spermatozoa was inhibited by the mitochondrial uncoupling agent carbonylcyanide-p-trifluoromethoxy-phenylhydrazone (FCCP). Theophylline + dibutyryl cyclic AMP also inhibited calcium uptake in the presence or absence of FCCP. Uptake of low concentrations of calcium (0 . 1 mM) was inhibited by the calcium ionophore A23187, but at high calcium concentrations the ionophore stimulated calcium uptake. These observations are explained in terms of a mechanism for the regulation of calcium uptake in spermatozoa based on competing mitochondrial and plasma membrane pumps. Uptake of 32P was also inhibited. These effects provide evidence that cyclic AMP plays a role in the transport of ions across the plasma membrane of spermatozoa.

No abstract