Measurement of activin B in human saliva and localization of activin subunits in rat salivary glands.

The present paper is the first report to demonstrate that measurable amounts of activin B are secreted into the saliva. The results show wide fluctuations in activin B concentrations during the menstrual cycle with peak values detected at the follicular phase. Estrogen replacement therapy was found to increase salivary activin B levels in post-menopausal subjects. The concentration in males was negligible. These data suggest that activin B concentrations in the human saliva may be under hormonal regulation and propose that salivary activin B measurements may prove useful in investigating the as yet less well defined local and/or physiological roles of activin B. The present paper reports, in addition, the immunohistochemical localization of activin/inhibin subunits in the duct systems of the rat submandibular, sublingual and parotid salivary glands.