Potato aspartic proteases (StAPs) exert cytotoxic activity on bovine and human spermatozoa.

OBJECTIVE

To evaluate the in vitro spermicidal activity of Solanum tuberosum aspartic proteinases (StAPs) on bovine and human sperm.

METHODS

Controlled laboratory study.

METHODS

Three research laboratories at a university of biologic science. ANIMAL(S) AND DONOR(S): Frozen semen from five Aberdeen Angus bulls and six proven fertile men volunteers.

METHODS

The effect of StAPs on sperm motility was studied in vitro by incubation of different concentrations of StAPs with sperm suspensions, and motility was assessed by direct microscopic observation. Membrane integrity was analyzed by SYTOX Green uptake after incubation with different StAP concentrations. The effect of StAPs was evaluated by human erythrocyte lysis, as a control in somatic cells. The StAPs binding was monitored by fluorescence.

METHODS

Total and progressive sperm motility; hypoosmotic swelling test and SYTOX Green uptake as a measure of membrane damage; fluorescein isothiocyanate-labeled StAP binding by an optical microscopy.

RESULTS

The StAPs reduced sperm motility in a dose-dependent manner, and 25 microM of StAP1 and 35 microM of StAP3 completely abolished the progressive motility. The StAPs were able to bind in the postacrosomal and midpiece region only in bovine sperm. Also, StAPs caused spermatozoa agglutination. In vitro cell toxicity was observed by a dose-dependent increase in hypoosmotic swelling negative sperm and SYTOX Green uptake in both human and bovine spermatozoa; however, no toxic effect was observed on erythrocytes.

CONCLUSIONS

The spermicidal effect of StAPs involves plasma membrane permeabilization.