Ultrastructural localization of uteroglobin immunoreactivity in rabbit lung and endometrium, and rat ventral prostate

Recent biochemical studies have demonstrated amino acid sequence homologies between uteroglobin from rabbit endometrium and prostatic binding protein from rat ventral prostate. We have studied the ultrastructural distribution of uteroglobin-immunoreactive material in rabbit lung and endometrium and rat ventral prostate using an uteroglobin antibody raised in guinea pigs. Secretory granules of bronchiolar Clara cells, endometrial non-ciliated cells and rat prostate secretory cells gave a positive immunoreaction when this antibody was used. The results indicate a close relationship of immunoreactive epitopes of proteins present in those secretory cells. The functional properties of these proteins (glycoproteins, steroid binding, androgen-dependent secretion) suggest a close functional relationship, for instance a surface action such as coating, capping, masking or lubrication.