【Objective】 To establish the rat prolactinomas model and to identify its stability. 【Methods】 Forty female Wistar rats were randomly divided into control group (group A

n = 10)

and experimental groups which were given injection of estradiol benzoate regularly for 8 weeks (group B

n = 10)

for 12 weeks (group C

n = 10) and withdrawal for 4 weeks after 12 weeks injection of estradiol benzoate (group D

n = 10). The change of body weight was recorded every 15 days and the rats were executed on the corresponding time to measure the pituitary weight as well as the morphology of tumor. The rat prolactinomas were identified by HE staining and prolactin (PRL) immunohistochemistry staining. We chose a rat for magnetic resonance imaging (MRI) when injected with estradiol benzoate at 8

12 weeks and at 4 weeks after withdrawal of estradiol benzoate to identify the model stability. 【Results】The body weights of the rats injected with estradiol benzoate increased slower than the control group accompanied with the depilation phenomenon after two weeks. Group B

group C

and group D emerging rate of tumor were 70%

100%

and 100%

respectively. The pituitary cells of the rats injected with estradiol benzoate showed hyperchromatic nucleus

disordered cell arrangement and a mass of vessels. The induced tumors were identified as prolactinomas by PRL immunohistochemistry staining since the number of the PRL positive cells in the estradiol benzoate treated groups was significantly higher than in the control group. The results of pituitary MRI showed that the pituitary volume increased gradually with the extension of estradiol benzoate induction time. No shrinkage of pituitary was observed after 4 weeks withdrawl of estradiol benzoate. 【Conclusion】 Intraperitoneal injection of estradiol benzoate could induce rat prolactinoma with high induction rate and stability.