Ação da tibolona no epitélio urogenital de ratas castradas

Abstract

The aim of this study is to determine the effect of prolonged use of tibolone in the urogenital epithelium of ovariectomized rats. Fourteen Wistar rats, aged 8 weeks and average weight of 250g, castrated 30 days before the experiment were used. On day 0 of the experiment, the rats from tibolone group (n=9) were treated per os with 1mg/day. Rats from the control group (n=5) received only the vehicle, 0.5% carboxymethylcellulose. Every week the rats were weighed and food intake was measured every 3-4 days. Vaginal cytology was performed in all rats on days 30, 0, 1 to 6 of the experiment and then every 30 days. Slides were immediately fixed in 95% alcohol and stained by the Papanicolaou technique. At 20 weeks of experiment the animals were anesthetized and sacrificed by cervical dislocation. The urogenital system was removed from each rat, and set at 10% buffered formalin, cleaved after 48 hours and processed for embedding in paraffin. Histological sections of 4µm from vagina, urethra and bladder were stained with hematoxylin and eosin, picrosirius red, PAS and PAS/diastase, and Weigert s resorcin fuchsin. Cell proliferation was analyzed by immunohistochemistry using the ki-67 marker. Furthermore, morphometric analyses were performed for epithelial thickness, percent area of collagen fibers and blood vessels, mast cells and ki-67 positive nuclei per mm basal membrane. Means and standard error of means were calculated in each group. The data were compared using the Mann-Whitney test, with significance level at P<0.05. In control group, all the vaginal smears were compatible to anoestrus till the end of experiment. In the tibolone group, from 3 days in all rats cytology was similar to estrus, which remained without major changes until the end. Significant lower daily food intake and body weight were found in the tibolone when compared to the control group (P<0.0001). In the vagina, epithelial thickness, number of ki-67 positive nuclei per mm basal membrane, number of vessels and number of mast cells were significantly higher in the tibolone group when compared to the control group. In the lower urinary tract, only the number of mast cells was significantly higher in the urethra of treated animals compared to controls. The content of glycogen and glycoproteins in the vaginal epithelium was modified by tibolone; alterations were less frequent in the urethral epithelium and no change was observed in the bladder epithelium. Tibolone administered in high doses and long-term has trophic effect in the vagina and has no dysplastic or neoplastic effect on vagina, urethra and bladder of castrated rats