Prolactin and Growth Hormone Synthesis and Thymidine Incorporation in Dissociated Rat Pituitary Tumor Cells

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Abstract
The effect of in vivo diethylstilbestrol (DES) treatment on the MtT/W15 transplantable pituitary tumor was examined in dissociated pituitary cells by measuring the rate of incorporation of [3H]thymidine into DNA and the synthesis of prolactin (PRL) and growth hormone (GH) as assessed by the rate of incorporation of [3H]leucine. MtT/W15 transplantable pituitary tumors from rats treated for 3 weeks with DES showed significant reduction in the extent of [3H]thymidine incorporation compared with tumor cells from untreated rats (2231 .+-. 182 vs 172 .+-. 17 dpm/105 cells; n = 3). In addition, tumor cells from DES-treated rats showed a significant increase in GH synthesis compared with tumor cells from untreated rats. In contrast to these findings, dissociated pituitary cells from non-tumor-bearing rats given 10 mg DES in Silastic tubing for 3 weeks showed a three-fold increase in PRL synthesis compared to cells from untreated control rats (29.3 .+-. 1.5 vs 10.0 .+-. 0.9% of total radioactivity in gel; n = 3). There was also a four-fold increase in the rate of [3H]thymidine incorporation after DES-treatment in non-tumor-bearing rats (695 .+-. 114 vs 178 .+-. 13.9 dpm/105 cells; n = 3). These results indicate that DES inhibits MtT/W15 pituitary tumor cell proliferation, while stimulating synthesis of GH.

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