Spermatotoxic effect of aflatoxin B1 in rat: extrusion of outer dense fibres and associated axonemal microtubule doublets of sperm flagellum

Male Wistar rats were treated with aflatoxin B1 (AFB1). Live as well as methanol-fixed cauda epididymal spermatozoa were stained with acridine orange (AO) and ethidium bromide (EB) and observed under a fluorescence microscope. Giemsa-stained smears were observed in a bright field microscope. Unstained smears were observed with phase contrast illumination. The axoneme of more than 10% of the spermatozoa of treated rats had the outer dense fibres (ODFs), in varying numbers, and the associated axonemal microtubule doublets of the flagellum extruded either at midpiece-principal piece junction or connecting piece. This could be perceived in all light microscopic preparations, but AO-EB staining offered an advantage of the assessment of the viability as well. TEM observation of sections of the testis and cauda epididymidis also revealed ODF extrusion, as seen in the transverse sections of sperm flagella missing one or more ODFs and the associated axonemal microtubule doublets. In a few such sections, the extruded elements were seen in the cytoplasm, outside the mitochondrial sheath or peripheral sheath. Marginal to severe mitochondrial pathologies were observed in the spermatozoa and elongated spermatids, suggesting a link between AFB1-induced sperm mitochondrial pathology and extrusion of ODFs. However, the possibility that AFB1 treatment would disrupt the cytoskeletal proteins of the flagellum, resulting in the extrusion of ODFs, cannot be excluded. This sperm abnormality is reported for the first time as produced by a dietary toxin. Dietary aflatoxins, therefore, could also be contributory factors for the deterioration of the reproductive health of men.