Objective: To compare the changes of the protein bcl-2 expression, regulatory mechanism in the process of apoptosis, in the secretory endometrium throughout natural and artificial (estrogen-progesterone substitution) cycles in the same group of patients. Design: A prospective study. Setting: Dept. of Obstetrics and Gynecology, University Hospital Olomouc, Dept. of Histology and Embryology, Faculty of Medicine, Palacký University in Olomouc, Dept. of Obstetrics and Gynecology, Bata Hospital, Zlín Methods: Endometrial samples (n=56) were obtained on days 5 and 7 after ovulation, progesterone addition, resp. Patients (n=14) included in the study had regular menstrual cycle, age under 40, BMI range 20–32 and basal FSH level range 5–9 IU/l. The collected samples were processed routinely and bcl-2 was estimated by indirect three level imunohistochemic method. Results: We demonstrated the bcl-2 expression in all evaluated layers (epithelial surface, stroma, glands) of the mid-secretory endometrium in both cycles. No difference was found in bcl-2 expression between days 5 and 7 in the secretory phase of the natural cycle. In artificial cycles higher bcl-2 expression was found only in epithelial surface (p<0.05) between days 5 and 7. On day 7 higher bcl-2 expression was found in the artificial cycle in the endometrial epithelial surface (p<0.001) as well as in spongy layer (p<0.01) and compact layer (p<0.05) comparing to day 7 of the natural cycle. Conclusion: The bcl-2 expression in the mid-secretory endometrium is significantly higher in the cycle with estrogen-progesterone substitution comparing to the natural cycle. These changes were more significant in endometrial and glandular epithelium than in stromal cells.

        Key words: protein bcl-2, endometrium, oral estrogen-progesterone substitution