Effect of tamoxifen on growth and prolactin secretion of rat pituitary tumours

Abstract

The antioestrogenic drug tamoxifen was administered to rats bearing transplanted prolactin-secreting tumours derived from spontaneously occurring pituitary adenomas in Wistar-Furth rats. Some inhibition of tumour growth was observed but this was accompanied by an increase in plasma prolactin concentrations. Bromocriptine, however, consistently inhibited both growth and prolactin secretion of these tumours. The addition of tamoxifen to bromocriptine treatment produced no increased response to the dopamine agonist. Tamoxifen increased prolactin secretion by tumour cells in vitro but did not affect DNA synthesis. Normal rats responded to tamoxifen with a moderate increase in plasma prolactin concentrations and there was no change in pituitary DNA synthesis.