Effect of prolonged use of high dose of tibolone on the vagina of ovariectomized rats.

The aim of this study was evaluate the effect of prolonged use of high dose of tibolone on the vagina of ovariectomized rats. Bilateral ovariectomy was performed on 14 rats weighing 250 g. Thirty days later, vaginal smears were collected verifying the menopause status by anoestrus cytology. Rats were divided randomly into groups: experimental rats (n = 9) received 1 mg tibolone/day orally and control rats (n = 6) received placebo (carboxymethylcellulose). After 150 days, all rats were sedated and euthanized by cervical displacement. The vagina was removed, fixed in 10% buffered formalin, sampled and processed for paraffin embedding. Histological sections were stained with haematoxylin and eosin, picrosirius red, periodic acid Schiff (PAS) and PAS-diastase, and Weigert's resorcin-fuchsin. Cell proliferation was analysed by immunohistochemistry to detect Ki67. Histomorphometric analyses were performed for epithelial thickness, per cent area of collagen fibres and blood vessels, mast cells and Ki67-positive nuclei per mm of basal membrane. Means and standard error of means were calculated, and data were compared using the Mann-Whitney test, with significance level at P < 0.05. In the vagina, epithelial thickness, number of Ki67-positive nuclei per mm of basal membrane, number of vessels and number of mast cells were significantly higher in the tibolone group when compared with the control group. Furthermore, the content of glycogen and glycoproteins in the vaginal epithelium was modified by tibolone. Tibolone administered in high dose and for a long period has a trophic effect, reversing vaginal atrophy, and has no dysplastic or neoplastic effect in the vagina of ovariectomized rats.

[Effect of high doses of tibolone in body weight and lipid profile of ovariectomized rats]. / Efeito de doses elevadas de tibolona sobre o peso corporal e perfil lipídico de ratas ooforectomizadas.

PURPOSE: to evaluate the effect of the prolonged use of a high dose of tibolone on the body weight variation and lipid profile of oophorectomized female rats. METHODS: 15 Wistar rats weighing 250 g were randomly divided into two groups. The Experimental Group (n=9) received 1 mg/day of oral tibolone. The Control Group (n=6) received daily 0.5 mL of 0.5% carboxymethylcellulose by gavage. Bilateral oophorectomy was performed 30 days before the beginning of the experiment. On day 0 of the experiment, the animals began to receive the respective treatment for 20 weeks. Body weight was controlled every seven days and food consumption was measured every three to four days along the experiment, in order to establish the daily mean consumption per animal. The results were compared by the Student's t-test, with the significance level set at p<0.05. RESULTS: the daily food consumption of the Tibolone Group was significantly lower (12.7+/-1.2 g, p<0.001) compared to the Control Group (14.5+/-1.4 g). This difference was also significant when the body weight was compared between the Tibolone and Control Groups (p<0.001), with the Tibolone Group having lower weight along the experiment. At the end of the experiment, the mean body weight was 215.6+/-9.3 g in the Tibolone Group and 243.6+/-6.4 g in the Control Group. Regarding the lipid profile, the Tibolone Group had significantly (p<0.001) lower total cholesterol compared to the Control Group (30.3 versus 78.6 mg/dL). The level of HDL-c was also significantly different (p<0.001), with the Tibolone Group showing lower levels than the Control Group (9.0 versus 52.0 mg/dL). No significant difference between the groups was registered in the other biochemical parameters examined (LDL-c, VLDL-c and triglycerides). CONCLUSIONS: tibolone causes a significant reduction of HDL-c and total cholesterol and has a deleterious effect on the body weight of oophorectomized rats, which may be related to the lower food ingestion by these animals.

[Effect of tibolone on endometrium of castrated rats]. / Efeito da tibolona sobre o endométrio de ratas castradas.

PURPOSE: to evaluate the effect of long-term use of a high dose of tibolone on the morphology of the endometrium of castrated female rats. METHODS: fifteen female Wistar rats, aged eight weeks and weighting about 250 g were used. All the female rats were submitted to bilateral oophorectomy and 30 days afterwards, vaginal cytology was collected, to verify the menopause status. The female rats were randomly divided in two groups. The Treatment Group (n=9) received 1 mg of tibolone/day orally; the Control Group (n=6) received a solution of carboxymethylcellulose vehicle. After 20 weeks of treatment, all the animals were sedated and sacrificed by cervical dislocation. The uterus was removed and fixated in 10% buffer formaldehyde. Both uterine horns were divided in three regions (proximal, medial and distal) and processed to be included in paraffin. Histological sections, stained with hematoxylin-eosin were submitted to morphological and morphometrical analysis. The following parameters have been analyzed: thickness of the endometrial superficial epithelium, thickness of the endometrium stroma, endometrial area, absolute number of endometrial glands and number of glands/endometrial area. The data obtained were compared by the t-Student test. RESULTS: in the Tibolone Group, the uteri were well developed and there was a significant increase (p<0.01) of all the histomorphometric parameters. In some cases, the cylindrical epithelium became stratified, pavimentous and covered the internal portions of the glands, as well as of the endometrium cavity. Rats from the Control Group presented uterine atrophy. There were few tubular-like glands and scarce intercellular substance. Glands were covered by cubic epithelium which extended itself to the endometrial cavity. CONCLUSIONS: high doses of tibolone, given for long periods of time to castrated female rats, have an estrogenic effect which can be dose-dependent, causing proliferation in the endometrium and causing changes in the cell differentiation (squamous metaplasia), but do not lead to hyperplasia.