DNA synthesis in rabbit spermatozoa after treatment with lysolecithin and fusion with somatic cells

Fusion of rabbit cauda epididymal or ejaculate spermatozoa with F5-1 Syrian hamster somatic cells in the presence of lysolecithin resulted in the formation of heterokaryocytes, initiated disaggregation of spermatozoal chromatin and stimulated DNA synthesis by the disaggregated chromatin. Fifteen to 20% of the F5-1 cells fused with 1 to 5 spermatozoa. Many of the spermatozoal nuclei were morphologically altered and appeared as ovoid, Feulgen-positive, clumps of dense material. These clumps, termed sperm bodies, exhibited a metachromatic response following acridine orange staining closely akin to that exhibited by definitive spermatozoal heads on the same preparations. Only the sperm bodies and spermatozoa exhibited autoradiographic labeling of nuclei following fusion of in vivo labeled rabbit spermatozoa with F5-1 cells. Incorporation of ³H-thymidine administered in vitro to cultures of heterokaryocytes indicated that DNA synthesis was initiated in the sperm bodies.