Studies on growth hormone secretion VI. Effects of dibutyryl cyclic AMP, prostaglandin E 1, and indomethacin on growth and hormone secretion by rat pituitary tumor cells in culture

Abstract

The growth of rat pituitary tumor cells (GH 1 line) maintained in monolayer culture was inhibited by dibutyryl cyclic AMP in a dose-related fashion. Neither PGE 1 (2.8 × 10 −5M) nor indomethacin (2.8 × 10 −6M) had any significant effect on cell proliferation. Release of GH into the culture medium was stimulated by the cyclic AMP derivative but not by PGE 1 or indomethacin. In short term experiments (15 min.) both in intact monolayers and in trypsin-treated cells incubated in suspension, PGE 1 caused a 2–10 fold increase in cyclic AMP levels. This response, however, appeared to be of short duration reaching a maximum in 10 minutes. It is suggested that, at least in this line of pituitary tumor cells, PGE 1 does not mimic the effect of cyclic AMP, for it probably cannot sustain the elevated intracellular levels of this nucleotide which seem to be necessary for growth inhibition and enhanced GH secretion.