Immunocytochemical study of peptidylarginine deiminase: localization of its immunoreactivity in prolactin cells of female rat pituitaries.

We have performed an immunocytochemical study of peptidylarginine deiminase (EC 3.5.3.15) in rat pituitaries. Male and female rat pituitaries were fixed by brief transcardial perfusion of Bouin Hollande Sublimate solution. Immunoperoxidase staining of cryosections obtained from female pituitaries with an antiserum to rat skeletal muscle peptidylarginine deiminase yielded specific staining of numerous cells in the pars distalis. In contrast, few immunopositive cells were noted in the pars distalis of male pituitaries. At least some of the immunopositive cells in female pars distalis were also stained with an antiserum to rat PRL. No such coincidence of immunoreactivities was noted when antisera to other anterior pituitary hormones were used. Biochemical and immunocytochemical examination of peptidylarginine deiminase during the pregnant period revealed its marked depletion on day 7 and its substantial restoration on day 14, showing apparently negative correlation with the known changes in the secretory activities of lactotrophs. This and the female-dominant occurrence of peptidylarginine deiminase in lactotrophs suggest significant involvement of the enzyme in the function of lactotrophs.