Cytoplasmic argyrophilic protein(s) in cumulus-oocyte complexes: a preliminary study

The presence of acidic argyrophilic protein(s) in cumulus cells and oocytes was examined in bovine, ovine, porcine and murine cumulus-oocyte complexes (COCs) using a specific silver-staining method. The COCs were isolated from small (1 mm) or large (3-5 mm) antral follicles; they were fixed immediately after slaughter (first group) or after transfer to the laboratory (ca 60 min, second group) and then silver stained according to Likovskí and Smetana (1981). The argyrophilic proteins were accumulated mainly in foot processes of cumulus cells on oocytes isolated from large bovine follicles. The intensity of the reaction was less evident in small follicles. The intensity of staining gradually disappeared from cumulus cells as the maturation continued. Moreover, we were unable to detect similar strong labelling in mouse, pig and sheep COCs. Such a chronology suggests that argyrophilic protein(s) may play a role in the transition from meiotic arrest to resumption in bovine oocytes. Our results also suggest that preliminary events of maturation may occur just after slaughter, ie a relatively long time before the COCs are isolated and cultured in vitro.