Changes in uterine steroid receptors after estrogen contraception in bitches.

摘要

The aim of the present study was to evaluate the effect of estradiol benzoate (EB) treatment on estradiol (E2) and progesterone (P4) in blood, and on estrogen (ER) and progesterone (PR) receptors in the uteri of mixed breed bitches. Injections of 10 micro g EB/kg (Mesalin, Intervet) and 100 micro g EB/kg (Oestradiolum benzoicum, Polfa) were given on day 3 and 5 after the first acceptance of males. Steroids were measured in samples collected from the vena cephalic using the immunofluorescent method. The average level of E2 was elevated to 190 and 260 pg/ml, respectively, and declined to control values within less than 12 days. An increase in P4 was observed only during the first 4 days. ER and PR were determined in uterine samples collected during hysterectomy performed on day 14 or 28 following the first EB injection. The radioligand assay was used for soluble (100.000 g cytosol) and structural (0.6 M NaCl extract) fractions. Typical binding characteristics for ER and PR were found in all analyzed samples. The amount of ER was unchanged over time in the untreated group, while PR significantly declined. The lower dose caused a 3-fold elevation of ER and PR (mainly soluble fractions) which on day 28 declined to control values with the exception of an uncompleted decline of soluble ER. The effect of higher doses on ER was only significant in its soluble fraction on day 14. However its influence on the PR (initially unchanged) occurred on day 28 and was elevated more than 10-times (mainly structural fraction). The results obtained indicate that uterine ER and PR responded differently to high and low doses of estrogen treatment.