Chronic effect of antidopaminergic drugs or estrogen on male Wister rat lactotrophs and somatotrophs

The aim of the present study was to evaluate the effect of antidopaminergic agents on the somatotrophs in the presence of hyperprolactinemia. Adult ma le Wistar rats were divided into 6 groups: a control group and five groups chronically treated (60 days) with haloperidol, fluphenazine, sulpiride, me toclopramide or estrogen. Somatotrophs and lactotrophs were identified by i mmunohistochemistry and the data are reported as percent of total anterior pituitary cells counted. The drugs significantly increased the percentage o f lactotrophs: control (mean a SD) 21.3 +/- 4.4, haloperidol 27.8 +/- 2.2, fluphenazine 34.5 +/- 3.6, sulpiride 32.7 +/- 3.5, metoclopramide 33.4 +/- 5.5 and estrogen 42.4 +/- 2.8. A significant reduction in somatotrophs was observed in animals treated with haloperidol (23.1 +/- 3.0), fluphenazine ( 22.1 +/- 1.1) and metoclopramide (24.2 +/- 3.0) compared to control (27.3 /- 3.8), whereas no difference was observed in the groups treated with sulp iride (25.0 +/- 2.2) and estrogen (27.1 +/- 2.8). In the groups in which a reduction occurred, this may have simply been due to dilution, secondary to lactotroph hyperplasia. In view of the duplication of the percentage of pr olactin-secreting cells, when estrogen was applied, the absence of a reduct ion in the percent of somatotrophs suggests a replication effect on this ce ll population. These data provide additional information about the direct o r indirect effect of drugs which, in addition to interfering with the dopam inergic system, may act on other pituitary cells as well as on the lactotro phs.