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Abstract
Purpose
The purpose of this study was to evaluate the effects of estrogen on detrusor contraction and the expression of muscarinic receptors in ovariectomized rats.
Materials and Methods
24 Sprague-Dawley female virgin rats (12 weeks old) were separated into three groups of 8 rats each. Group I served as a control group, group II was the ovariectomized only rats (Ovx group) and Group III was given estradiol benzoate (0.8mg/kg/day) subcutaneously for 7 consecutive days, beginning 1 week after ovariectomy (Ovx+E group). At the end of the experimental period, each rat was sacrificed and the urinary bladder was removed for contractile studies. The expressions of M2 and M3 receptors in the bladder epithelium and the muscle layer were investigated by performing immunofluorescent staining.
Results
The Ovx group showed a significantly decreased bladder contractile function on the KCl and carbachol-induced contractile tests, whereas the Ovx＋E group showed increased contractility (p＜0.05). The Ovx＋E group showed an increase of smooth muscle compared to the other groups. Ovariectomy induced a significant increase in the M3 receptors density in the bladder body, as compared to the control group (p＜0.05) but there was no significant difference between the Ovx group and the Ovx+E group.
References
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Fig. 1.
KCl 50mM induced contractile response of the rat bladder. The ovariectomized (Ovx) group showed a decreased contractile response to KCl 50mM compared with the control group and the Ovx＋estradiol treated (Ovx＋E) group. Each bar is the mean±SE. ∗: significantly different from the control group and the Ovx＋E group (p＜0.05).
Fig. 2.
Carbachol (Cch) induced contractile responses of the rat bladder. The ovariectomized (Ovx) group showed decreased contractile responses to Cch, as compared with the control group and the Ovx＋estradiol treated (Ovx＋E) group. Values are plotted as means±SE. ∗: significantly different from the control group and the Ovx＋E group (p＜0.05).
Fig. 3.
Representative photomicrographs showing staining of the control group (A), the Ovx group (B) and the Ovx＋E group (C). The connective tissue in the Ovx group was markedly increased (white arrow) more than that in the control group and the Ovx+E group. Smooth muscle hypertrophy was observed in the Ovx＋E group (black arrow) (H&E stain, original magnification, x40).
Fig. 4.
Comparisons of the M3 and M2 receptor expressions among the three groups on the immunofluorescent study. The expressions of M3 (green) and M2 (red) were showed in the control group (A, B), the Ovx group (D, E) and the Ovx＋E group (G, H). Merged images of the M3 and M2 were showed in the control group (C), the Ovx group (F) and the Ovx＋E group (I). The M3 receptor expressed in the epithelial area (arrow), and the M2 receptor had a similar pattern. The M3 receptor was more strongly expressed in the Ovx＋E and Ovx groups than that in the control group. The M2 receptor was more strongly expressed in the Ovx＋E group than that in the Ovx group and the control group (original magnification, x400).
Table 1.
Comparisons of the M2 receptor expression among the three groups
| Group | Density of M2 receptor | |
|---|---|---|
| Epithelial layer | Muscle layer | |
| Control | 82.2±3.7 | 55.4±2.1 |
| Ovx | 94.2±4.1 | 56.2±1.5 |
| Ovx＋E | 113.2±6.0∗† | 63.6±2.3∗† |
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