AGE-RELATED INCREASE IN PEPTIDYLARGININE DEIMINASE IN THE MALE-RAT PITUITARY

We have measured the activity of peptidylarginine deiminase (EC 3.5.3. 15) in male Wistar rat pituitaries at various ages. Pituitaries obtain ed from 3- and 9-month-old rats showed negligible activities. The mean enzyme activity increased appreciably by 18 months and markedly by 24 months accompanied with actual increases in the enzyme content. The p eptidylarginine deiminase mRNA content showed a similar but more gradu al increase appreciable from 9 months. Many enzyme-positive cells were present in the pars distalis of 24-month-old male pituitaries. Most o f the enzyme-positive cells coincided with lactotrophs. The pituitary prolactin content showed a gradually increasing profile resembling tha t of the enzyme mRNA, but the serum prolactin concentration did not in crease significantly. Neither the serum 17 beta-estradiol content nor the pituitary estrogen receptor content showed significant variation t hat could account for the marked increase in the pituitary enzyme cont ent between 18 and 24 months of age. These data suggest possible prese nce of other factors regulating the enzyme content in, old male pituit aries.