INTERACTION BETWEEN PC12 LIPOSOMES ENCAPSULATING ATP AND HUMAN SPERMATOZOA

In a preliminary report (Skiba-Lahiani, M. et al.), we showed that dil auroylphosphatidylcholine (PC12) liposomes entrapping ATP sustain sper m motion over time and in some experiments a concomittant increase in the percentage of human acrosome-reacted spermatozoa. With the present study, we confirmed an interaction between PC12 liposomes and human s permatozoa vizualizing the morphologic aspects when we used several ul trastructural techniques. Investigations using on the one hand liposom es made from fluorescently labeled phosphatidylcholine analogue, trobe nz-2-oxa-1,3-diazol-4-yl)-phosphatidylcholine (Acyl-NBD-PC), and on th e other hand liposomes encapsulating a fluorochrome (calceine), allowe d to approach the mode of this interaction. Electron-microscopic exami nation has shown on the one hand the transfer of Acyl-NBD-PC from vesi cles to cells, and on the other hand the transport of encapsulated flu orochrome (calceine) into the cell, supporting the suggestion of membr ane perturbation as a cause of an increase of its permeability to trig ger the acrosomal exocytosis. Under conditions which stimulate the acr osome reaction by liposomes entrapping ATP (L-ATP) and blank liposomes (L-B) treatments, we have not shown an increase in intracellular calc ium when we used the fluorescent probe ofuran-5-oxy]-2-(2'-amino-5'-me thylphenoxy)-ethane N,N,N',N'-tetraacetic acid] (Fura-2) suggesting th at the interaction PC12 liposomes-human spermatozoa induced an acrosom e reaction different: from the physiologic acrosome reaction. (C) 1998 Elsevier Science B.V. All rights reserved.