Effects of filipin, digitonin, and polymyxin b on plasma membrane of ram spermatozoa--an EM study.
The effects of three membrane-active agents, filipin, digitonin, and polymyxin B on the plasma membrane of ram spermatozoa have been studied by freeze-etch electron microscopy. Filipin and digitonin both reacted with cholesterol and caused visible membrane modification in cholesterol-rich regions, with filipin being a more specific agent than digitonin. Polymyxin B, which is known to interact specifically with negatively charged phospholipids of bacterial membranes, exhibited a selective binding and subsequent modification of sperm plasma membranes. This binding was shown to be inhibited in the presence of 1 mmol/1 Ca2+. We hence propose that both filipin and polymyxin B are useful cytological markers for specific biological molecules in eukaryote membranes--filipin for cholesterol, and polymyxin B for negatively charged phospholipids.
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects*; D002784:Cholesterol / Q000032:analysis; D004072:Digitonin / Q000494:pharmacology*; D005372:Filipin / Q000494:pharmacology*; D005613:Freeze Etching; D008297:Male; D008854:Microscopy, Electron; D010743:Phospholipids / Q000032:analysis; D011090:Polyenes / Q000494:pharmacology*; D011112:Polymyxin B / Q000494:pharmacology*; D011113:Polymyxins / Q000494:pharmacology*; D012756:Sheep; D013094:Spermatozoa / Q000187:drug effects* / Q000648:ultrastructure
D010743:Phospholipids; D011090:Polyenes; D011113:Polymyxins; D005372:Filipin; D002784:Cholesterol; D011112:Polymyxin B; D004072:Digitonin