Immunocytochemical identification of actin in rabbit spermiogenesis and spermatozoa

Actin was localized in testicular spermatids and in spermatozoa of rabbit by using a monoclonal anti-actin antibody and a specific antiserum against actin, labeled with colloidal gold. The antibody reactivity with sperm homogenates was determined by immunoblotting of one-dimensional gels. With on-grid postembedding immunostaining of Lowicryl K4M sections, actin was identified in the subacrosomal region of differentiating spermatids, and in four bulges situated between the inner acrosomal membrane and the nuclear envelope and in the anterior part of the postacrosomal region of ejaculated spermatozoa. Sperm actin was identified on two-dimensional gels as two spots in the isoelectric point and molecular weight corresponding to gamma and beta-isoforms of actin. Immunoblots stained with specific antibodies demonstrated that rabbit spermatozoa express gamma and beta-actin isoforms.