Immunological evidence of uteroglobin (blastokinin) in the male reproductive tract and in nonreproductive ductal tissues and their secretions.

Uteroglobulin (blastokinin) has been thought to be localized in the female reproductive tract, where it has been presumed to play a significant role in preimplantation events during early pregnancy. Employing two antisera in three test systems, immunological evidence now demonstrates the presence of the uteroglobin antigen in the male genital tract of the rabbit, viz., in vas deferens tissue extracts and secretions, cauda epididymal extracts and seminal plasma. Furthermore, components of the male and female reproductive tracts of the human, viz., seminal plasma and progestational endometrial extracts and uterine and oviducal secretions, contain proteins which crossreact with identity with anti-rabbit uteroglobin. Uteroglobin is undetectable in serum and in all rabbit non-reproductive tissue extracts in which it was sought, with the exception of two organ systems comprised of ductal structures, the respiratory and digestive tracts. Rabbit tracheal, bronchial and lung tissue extracts and secretions, esophageal tissue extracts and secretions and jejunal secretions, all contain an antigen indistinguishable from and presumably identical to uteroglobin. Thus, uteroglobin is not exclusively a female reproductive tract protein; it is also present in the male genital tract of both rabbit and human and in certain nonreproductive tissues and their secretions. These findings broaden the scope of possible biological functions of this protein, beyond events within the uterus during early pregnancy.