ESTROGEN REGULATES PEPTIDYLARGININE DEIMINASE LEVELS IN A RAT PITUITARY CELL-LINE IN CULTURE

A Nonidet P‐40 extract of growth hormone‐producing rat pituitary MtT/S cells was found to contain peptidylarginine deiminase (EC 3.5.3.15), which was indistinguishable from an enzyme preparation from rat muscle in Western immunoblotting and immunoprecipitation. This enzyme was immunocytochemically detected in the cytoplasm but was not secreted into the medium during the cultivation. When the cells were cultured for 2 days with various concentrations of 17 β‐estradiol (E2), the enzyme activity increased in a dose‐dependent manner, reaching a maximum level (four‐ to five old higher than control) at about 10−9 M. This increase in the enzyme activity was evident by 14 hr of culture and became relatively stable after 24 hr. It correlated well with the increase in the amount of the muscle type enzyme per cell as analyzed by Western immunoblotting. Estriol and a synthetic estrogen, diethylstilbestrol, also increased the enzyme activity, whereas testosterone, progesterone, and corticosterone were without effect. An antiestrogen, tamoxifen, which by itself was inactive, partially suppressed the effect of E2. Exposure of MtT/S cells for 14 hr to E2 increased incorporation of 35S‐labeled amino acids into the immunoprecipitable peptidylarginine deiminase. This increase was dependent on the concentration of E2, attaining a maximum level (about tenfold higher than the control) at about 10−9 M. These results indicate that estrogen effects the increase in peptidylarginine deiminase content in the pituitary cells by stimulating enzyme synthesis. Copyright © 1990 Wiley‐Liss, Inc.