Sertoli cells from newborn calf testis will be isolated, separated and grown in cell culture without the addition of serum, but with the addition of growth factors and hormones aimed at maintaining these cells in a differentiated state. Media from these cells, which will contain secreted proteins, will be concentrated and analyzed for the presence of Mullerian Inhibiting Substance, a glycoprotein. Detection of Mullerian Inhibiting Substance will be done with an organ culture bioassay. This glycoprotein will be characterized and isolated using electrophoresis, isoelectric focussing, and column chromatography. Purification of this protein will permit the development of an antibody against the protein and production of a radioimmunoassay.