PATHOMORPHOLOGICAL AND IMMUNOHISTOCHEMICAL STUDIES ON SPONTANEOUS NEOPLASTIC LESIONS IN WISTAR RATS
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Date
2013
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AAU, Anand
Abstract
Untreated CRL Wistar rats (40 males and 77. females) used to study the incidences of spontaneous neoplastic lesions during their life span of 2 years. Animals were kept in an environmentally controlled room with 22 ± 3°C temperature and 30- 70% humidity. Light/dark cycle of 12/12 hours with 300-400 lux was provided throughout the study period. Various parameters like survival, terminal body weight, hematology and biochemistry alterations and incidence of major spontaneous neoplastic lesions have been analyzed and compared with other surveys. The special staining procedure of Masson's Trichrome and Periodic Schiff stain (PAS) as well as iramunohistochemistry with S100 and Vimentin stain were performed for differential diagnosis of various tumors. The results of study showed, mean survival rate of 97.5 % for males and 98.7 % for females at 12 months age. Mean survival rate at the end of 24 months decreased markedly with 57.5 % in males and 68.8 % in females indicating that female rats had lower mortality than male rats. The body weights of experimental animals were taken at initiation, at 12 months and at 24 months of study. The terminal body weight (TBW) revealed a mean value of 669.5 g (range 561 to 778 g) in males and 516.8 g (range 358 to 649 g) in females. The TBW of current study animals was found to be quite stable over the time and homogeneous.The body weight , hematology and biochemical parameters of the single, multiple and major tumor (type of tumor having incidences >10 %) comprising animals were compared with the normal animals (animals without tumors) in both sexes. The increase (P<0.05) in body weight of female animals comprising the mammary gland fibroadenoma was noticed during interim body weight comparation. However, decrease in the terminal body weight of female animals comprising multiple tumors noticed during multiple comparison of body weights at different time periods. In male the body weight was comparable with the normal animals or animals not having any tumor. There were no significant changes between male and female noticed in haematological and biochemical parameters studied in relation to tumor development during terminal analysis. An increase in triglyceride (P<0.01) levels (mg/dl) (Male 136.51±10.62 vs Female 267.26 ±43.68) was noticed in female animals. Multiple comparision of biochemical parameters for single, multiple and major tumor comprising animals did not reveal any significant changes except a decrease in glucose levels noticed in female comprising single tumor. In current study analysis of 117 CRL Wistar Rats (40 males and 77 females) revealed that 47.5% of males and 67.5 % of females had one or several tumors. Total percentage of benign neoplasm were 78.9 % in male and 76.9 % in female while malignant neoplasm were noticed in 21.1 % and 23.1 % in male and female respectively. Benign tumors were more numerous than malignant tumors in both sexes. The major neoplastic lesions were found in the endocrine, integumentary and reproductive systems. Pituitary adenoma was the most frequent neoplasm which occurred in 23.7% of the males and 26.4 % of the female rats. The other most frequent tumors in males were Leydig cell tumor (10.5 %), benign pheochromocytoma (5.3%), thyroid C-cell adenoma (5.3 %), pancreatic islet cell adenoma (2.6 %), subcutaneous fibrosarcoma (5.3 %), subcutaneous fibroma (5.3%), and cutaneous keratoacanthoma (2.6%). In females, the other highest incidences were mammary fibroadenoma (24.8 %), uterine endometrial stromal polyp (16.0 %), endometrial adenoma (4.0 %), mammary adenoma with atypia (4.0 %), mammary adenocarcinoma (2.4 %), benign thymoma (2.4 %), subcutaneous fibrosarcoma (1.6%) and thyroid C-cell adenoma (0.8 %). All these data were compared to previously published historical control data. This retrospective analysis was undertaken in order to create historical data base and to study and diagnosed the various neoplastic findings.
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VETERINARY PATHOLOGY, A STUDY