During the past year, we have developed the first in vitro bioassay system for qualitative and quantitative analysis of the testis stimulating factor. Until now, the only method for determining the pres,ice of the testis stimulating factor utilized testicular artery and vein catheterization of intact cynomolgus monkeys. We are currently using this method to isolate the factor and to begin to study its physiology. During the next year, we hope to isolate the factor, develop antibodies to allow us to better measure it and to begin to look for the gene responsible for the factor. This is a very interesting factor because it is able to stimulate virilization as well as spermatogenesis in the absence of gonadotropins.
