Identification of spectrin and calmodulin in rabbit spermiogenesis and spermatozoa.

Actin was localized in the four subacrosomal bulges (Camatini et al., Eur. J. Cell Biol. 45:276-281, 1987), which characterize the sperm head of rabbit spermatozoa (Phillips, J. Ultrastruct. Res. 38:591-604, 1972), and in the postacrosomal region (Welch and O'Rand, Dev. Biol. 109:411-417, 1985; Camatini et al., Eur. J. Cell Biol. 45:276-281, 1987). Specific antibodies and indirect immunogold labelling on testis Lowicryl K4M sections and spermatozoa cryosections were used to study the distribution of calmodulin and a spectrin-like protein. This protein was also present close to the shaping membranes of the head. The results presented suggest a membrane-cytoskeletal role of actin, spectrin, and calmodulin.