DNA synthesis in immunreactive glandular cells in pituitary intermediate lobe cultures

Cell suspensions were prepared from adult rat pituitary intermediate lobes and grown in medium TC 199 supplemented with foetal calf serum. 7 or 8 days old cultures were pulse labelled with tritiated thymidine and thereafter processed for immunostaining using an antiserum against a synthetic alpha-1-28-ACTH-analogue. Immunreactivity was mainly confined to epithelial cells, but some spindle-shaped cells were also immunopositive. Thymidine incorporation was observed in some immunpositive cells which shows that cells committed to hormone production may enter the mitotic cycle.