[Pathologic changes of spontaneous tumors in Sprague-Dawley and Wistar rats].

Objective: To investigate the spontaneous neoplastic lesions and their incidences in Sprague-Dawley (SD) and Wistar rats, and to accumulate background data for carcinogenicity studies. Methods: One hundred and eighty SD rats and 240 Wistar rats (4-week old) , half in each sex, were used in this study. The rats were housed routinely under specific pathogen-free environment and euthanized after 104 weeks. Histopathological examination was undertaken for all animals including deaths and scheduled euthanasia. The types and incidences of spontaneous tumors were gathered statistically. Results: Total 411 rats (176 SD rats and 235 Wistar rats) were examined in this study. The total tumor incidence of the 411 rats was 57.7%(237/411). The total tumor incidence in SD rats was 55.7%(98/176), benign tumor incidence was 48.9%(86/176) and malignant tumor incidence was 15.9%(28/176). The total tumor incidence in Wistar rats was 59.1%(139/235), benign tumor incidence was 51.5%(121/235) and malignant tumor incidence was 14.5%(34/235). The main benign tumors were pituitary adenoma (23.3% in SD rats, 12.3% in Wistar rats), breast fibroadenoma (21.3% in SD rats, 12.9% in Wistar rats) and breast adenoma (16.9% in SD rats, 9.5% in Wistar rats) in females; testis Leydig cell tumor (0 in SD rats, 14.3% in Wistar rats) in males. The main malignant tumors were breast carcinoma (10.1% in SD rats, 3.4% in Wistar rats) and uterine leiomyosarcoma (0 in SD rats, 2.6% in Wistar rats) in females; squamous cell carcinoma of skin (2.3% in SD rats, 0.9% in Wistar rats); subcutaneous fibrosarcoma (1.1% in SD rats, 2.1% in Wistar rats); brain malignant glioma (1.1% in SD rats, 1.7% in Wistar rats). Conclusions: In the study, a high incidence of spontaneous tumors is reported in both SD and Wistar rats housed for 2 years. The incidence of benign tumors is higher than that of malignant rumors. The benign tumors mainly are pituitary adenoma, breast fibroadenoma and breast adenoma in females, and testis Leydig cell tumor in males. The malignant tumors mainly are breast carcinoma and some soft tissue sarcomas. The results of the study enrich the data of spontaneous tumor in SD and Wisar rats and provide background data for carcinogenicity studies for new drugs.目的：观察SD和Wistar大鼠自发性肿瘤病变及其发生率，为进一步开展致癌实验积累背景数据。 方法：采用4周龄无特定病原体(specific pathogen free，SPF)级SD大鼠180只和Wistar大鼠240只，雌雄各半，在SPF级环境下常规饲养104周后实施安乐死，对死亡动物及安乐死动物进行组织病理学观察，统计自发性肿瘤的类型和发生率。 结果：实际观察了411只大鼠(SD大鼠176只，Wistar大鼠235只)，患瘤动物占57.7%(237/411)。SD大鼠中患瘤动物占55.7%(98/176)，发生良性肿瘤的动物占48.9%(86/176)，发生恶性肿瘤的动物占15.9%(28/176)；Wistar大鼠中患瘤动物占59.1%(139/235)，发生良性肿瘤的动物占51.5%(121/235)，发生恶性肿瘤的动物占14.5%(34/235)。高发的良性肿瘤主要有垂体腺瘤(SD大鼠占23.3%、Wistar大鼠占12.3%)，雌性大鼠的乳腺纤维腺瘤(SD大鼠占21.3%、Wistar大鼠占12.9%)，雌性大鼠的乳腺腺瘤(SD大鼠占16.9%、Wistar大鼠占9.5%)，雄性大鼠的睾丸间质细胞瘤(SD大鼠占0，Wistar大鼠占14.3%)。高发的恶性肿瘤主要有雌性大鼠的乳腺癌(SD大鼠占10.1%、Wistar大鼠占3.4%)，雌性大鼠的子宫平滑肌肉瘤(SD大鼠占0、Wistar大鼠占2.6%)，皮肤鳞状细胞癌(SD大鼠占2.3%、Wistar大鼠占0.9%)，皮下纤维肉瘤(SD大鼠占1.1%、Wistar大鼠占2.1%)，大脑恶性胶质细胞瘤(SD大鼠占1.1%、Wistar大鼠占1.7%)。 结论：饲养104周的SD和Wistar大鼠，自发性肿瘤的发生率均较高。良性肿瘤的发生率高于恶性肿瘤。高发良性肿瘤主要为垂体腺瘤、乳腺纤维腺瘤(雌性动物)、乳腺腺瘤(雌性动物)、睾丸间质细胞瘤(雄性动物)；高发恶性肿瘤主要为乳腺癌(雌性动物)以及某些软组织肉瘤。本实验结果丰富了现有SD和Wisar大鼠自发性肿瘤的数据资料，为开展新药致癌实验提供了背景数据。.