Echistatin, a disintegrin, inhibits sperm-oolemmal adhesion but not oocyte penetration.
OBJECTIVE
To study the effects of echistatin, a disintegrin known to block the binding of fibronectin (FN) and vitronectin to their respective integrin receptors, alpha 5 beta 1 and alpha v beta 3, on the adhesion of human spermatozoa to the oolemma of zona-free hamster eggs and their subsequent penetration.


METHODS
Motile capacitated human spermatozoa and zona-free hamster eggs were coincubated in the presence of echistatin or in its absence and observed at short serial intervals. Whole mounts of these eggs, washed out of sperm suspension and stained with acridine orange, were scored for numbers of oolemmal adherent and penetrating sperm.


METHODS
University Hospital laboratories.


METHODS
Known fertile semen donors.


METHODS
Numbers of spermatozoa adherent to the oolemma and those penetrating the oocyte.


RESULTS
Sperm adherence to the oolemma was reduced significantly at micromolar concentrations of echistatin, in a concentration-dependent manner. In contrast, echistatin did not inhibit the penetration of oocytes by sperm that had become adherent to the oolemma despite the presence of echistatin.


CONCLUSIONS
We propose that two processes occur in the binding of sperm to the oolemma, one that is echistatin sensitive and possibly involving the integrin receptors that recognize FN and vitronectin, and a second process, resistant to echistatin, that leads to gamete membrane fusion.
Bronson
R A
RA
Department of Obstetrics and Gynecology, SUNY, Stony Brook 11794-8091, USA.
Gailit
J
J
Bronson
S
S
Oula
L
L
D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D002478:Cells, Cultured; D006224:Cricetinae; D005260:Female; D006801:Humans; D016023:Integrins / Q000502:physiology; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D008561:Membrane Fusion / Q000187:drug effects; D008647:Mesocricetus; D010455:Peptides / Q000494:pharmacology*; D013084:Sperm-Ovum Interactions / Q000187:drug effects*
D016023:Integrins; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; C057986:echistatin