Insulin-sperm interaction: effects on plasma membrane and binding to acrosome.
In in vitro studies, viable, intact human spermatozoa took up free radioinsulin with an apparently non-receptor-mediated mechanism. However, when a colloidal gold-insulin complex was substituted for the radiotracer, no surface binding was visualized at the ultrastructural level. Upon sperm incubation in the presence of free insulin, a dose-dependent release of phospholipid phosphorus occurred, with a concomitant derangement of head cell membrane. After head membrane removal, spermatozoa-bound radioinsulin in a time- and concentration-dependent manner, the binding was displaceable by unlabeled insulin, and an exclusive localization of the colloidal gold-insulin complex was visualized at the acrosome level. On the basis of this evidence, both the plasma membrane and the acrosome seem to represent cytological targets for insulin.
Silvestroni
L
L
Department of Experimental Medicine, University of Rome, La Sapienza, Italy.
Modesti
A
A
Sartori
C
C
D000177:Acrosome / Q000737:chemistry*; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D008297:Male; D011869:Radioligand Assay; D011972:Receptor, Insulin / Q000032:analysis*; D013094:Spermatozoa / Q000737:chemistry* / Q000648:ultrastructure; D013552:Swine
D007328:Insulin; D011972:Receptor, Insulin