Nucleolar inhibition in prolactin cells after combined thyroid hormone plus lisuride treatment in estrogenized rats

The growth reaction of the rat adenohypophysis to estradiol was previously found to be potentiated by dopaminergic antagonists (perphenazine) and inhibited by thyroid hormones and dopaminergic agonists. In the present experiment a combination of estradiol, lisuride and thyroid hormones was tested. Sixty male Wistar rats were divided into 6 groups: 1. controls; 2. estradiol benozate (E) in aqueous microcrystal suspension 1 mg/rat twice a week; 3. Thyreoidin (SPOFA) 0.2% in the food (T); E + T; 5. E + lisuride (N-D-6-methyl-8-isoergonelyl)-N'N-diethyl carbamide hydrogen maleate, 200 micrograms/rat per day in the food (L); 5. E + T + L. After 3 weeks the adenohypophysial weights, histology (PAS Orange G, indirect immunoperoxidase technique) and electron microscopic morphometry were examined. The increase in adenohypophysial weight was inhibited by T, L and significantly more by the combination T + L. The increased incidence of prolactin cells after estradiol was inhibited by T and L and equally by the combination T + L. The effect of both inhibitory substances (T + L) was also additive on the relative size of the nucleoli of PRL cells: marked nucleolar inhibition similar to that produced by cytostatics was observed in the E + T + L group of animals.