Description
Introduction: Inhibin is a peptide that is an inhibitor of FSH synthesis and secretion, and participates in the regulation of the menstrual cycle. Inhibin contains an alpha and beta subunit linked by disulfide bonds. Two forms of inhibin differ in their beta subunits (A or B), while their alpha subunits are identical. Inhibin belongs to the transforming growth factor-beta (TGF-beta) superfamily. In women, FSH stimulates the secretion of inhibin from the granulosa cells of the ovarian follicles in ovary. In turn, inhibin suppresses FSH.Inhibin secretion is diminished by GnRH, and enhanced by insulin-like growth factor-1 (IGF-1). Inhibins have been defined based on their activity of suppressing pituitary gonadotropin secretion. Thus, the serum concentrations of Inhibin B and FSH are inversely correlated, and at low serum levels of Inhibin B, FSH concentration goes up. Inhibin B serum concentration increases gradually in the follicular phase to a broad peak at 7 days prior to the LH surge, and may constitute the limiting factor for the duration of the inter-cycle FSH rise. A decrease and a second peak follow this peak one-day past the LH surge. Most of the serum Inhibin B concentration originates from large follicles, since such follicles secrete 10 fold higher concentrations than do the small follicles. Inhibin B concentrations drop to a very low concentration at the luteal phase, and is undetectable during pregnancy.
Principle of the Assay: The microtiter plate provided in this kit has been pre-coated with goat-anti-rabbit antibody. Standards or samples are then added to the appropriate microtiter plate wells with a Horseradish Peroxidase (HRP)-conjugated INH-B and antibody preparation specific for INH-B, and incubated. Then substrate solutions are added to each well. The enzyme-substrate reaction is terminated by the addition of a sulphuric acid solution and the color change is measured spectrophotometrically at a wavelength of 450 nm +/- 2 nm. The concentration of INH-B in the samples is then determined by comparing the O.D. of the samples to the standard curve