Recovery of rat prolactin cells following cessation of estrogen treatment

Abstract

Estrogen treatment for one month in female rats caused some regression of somatotrophs, but induced an increase in the number of prolactin cells and caused these cells to hypertrophy. These stimulated prolactin cells showed extensive development of the granular endoplasmic reticulum which was often arranged in concentric whorls (Nebenkern). Most of the prolactin cells contained a small number of mature granules which were smaller in size than those of prolactin cells in control animals. These prolactin granules were round in sectioned profile and closely resembled the secretory granules of normal somatotrophs.

PIP: The recovery of rat prolactin cells following cessation of estrogen treatment is described. The ultrastructural changes induced by estrogen treatment in prolactin cells were observed and the recovery of these stimulated cells were followed for periods ranging from 20 hours to 15 days posttreatment. Treatment for 1 month caused some regression of somatotrophs in female rats, but induced an increase in the number of prolactin cells and caused these cells to hypertrophy. The stimulated prolactin cells showed extensive development of the granular endoplasmic reticulum which was often arranged in concentric whorls (Nebenkern) and most cells contained some small mature granules. 5-10 days after suspension of treatment many prolactin cells contained numerous secretory granules ranging in size from 150 to 500 mm. Only the largest (750 mm) exhibited the irregular shape characteristic of mature granules in normal prolactin cells. 15 days posttreatment most prolactin cells exhibited numerous secondary lysosomes and the mature secretory granules were similar in morphology to those of normal prolactin cells. Since the somatotrophs appeared not to be stimulated by the treatment it is difficult to accept the concept that somatotrophs can undergo transformation into prolactin cells.