The isolation of polypeptides with FSH suppressing activity from bovine follicular fluid which are structurally different to inhibin

Three proteins (31, 35 and 39kDa) with inhibin-like activity have been isolated from bovine follicular fluid with identical NH 2-terminal amino acid sequences. These polypeptides are distinct from inhibin, based on their different NH 2-amino acid sequence, molecular masses, absence of a subunit structure, absence of inhibin immunoactivity and the failure of inhibin antiserum to neutralize their bioactivity in vitro . Their inhibin-like biological activities based on their ability to suppress FSH cell content by pituitary cells in culture are 5–10% of bovine 31kDa inhibin.