THE N-TERMINAL PEPTIDE OF THE INHIBIN ALPHA-SUBUNIT - WHAT ARE ITS ENDOCRINE AND PARACRINE ROLES

alpha N inhibin (molecular mass 23/24 kD) is present in the pro-alpha N-alpha C subunit of inhibin and can be released by cleavage at the fl anking arginine residues during posttranslational processing. Although the alpha N protein isolated from bovine follicular fluid has no inhi binlike (FSH suppressing) activity, alpha N is present in high molecul ar weight forms of biologically active inhibin found in follicular flu id and plasma. alpha N may modify the biological activity of inhibin b y influencing its half-life or access to ifs receptor. alpha N may als o play a role in regulating fertility through a local action on ovulat ion by the ovary that is independent of the actions of inhibin. The ev idence suggests a unique physiological significance for the precursor peptides of the inhibin-alpha subunit in both the endocrine and paracr ine control of fertility.