Differential estrogen-related responses in myofiber cross-sectional area of pelvic floor muscles in female rats

Abstract

Objective

To determine the role of estrogens in myofiber cross-sectional area (CSA) of the pubococcyegeus (Pcm) and iliococcygeus muscles (Icm).

Methods

In Experiment 1, we excised the Pcm and Icm during the metestrus and proestrus stages of the estrous cycle to measure the myofiber CSA. In Experiment 2, we allocated other rats into the following groups: sham (Sh), ovariectomized (OVX), OVX plus 1,4,6-androstatriene-3,17-dione (ATD; OVX + ATD), an aromatase inhibitor, and OVX plus estradiol benzoate (OVX + EB). We carried out appropriate statistical tests to determine significant differences (p ≤ 0.05) in variables measured for both Experiments.

Results

The Pcm myofiber CSA at proestrus was higher than at metestrus, while the Icm myofiber CSA did not change. Ovariectomy increased the Pcm myofiber CSA, which was exacerbated with the ATD administration. The EB supplementation successfully reversed the ovariectomy-induced enlargement of the CSA. No significant changes were detected for the Icm myofiber CSA.

Conclusions

Fluctuating ovarian steroid levels at the estrus cycle significantly influence the CSA myofiber of the Pcm but not that of the Icm. Estrogen actions, having a gonadal or extragonadal origin, influence importantly the CSA of the Pcm.

摘要

目的：探讨雌激素在耻骨尾骨肌（Pcm）和髂尾骨肌（Icm）肌纤维截面积（CSA）中的作用。

方法：实验1在发情周期的传情期和发情前期切除Pcm和Icm, 测量肌纤维CSA。实验2将其他大鼠分为假手术组（Sh）、去卵巢组（OVX）、OVX + 1,4,6-雄甾三烯-3,17-二酮组（ATD；OVX＋ATD）, 芳香酶抑制剂, 以及OVX +苯甲酸雌二醇（OVX＋EB）。我们进行了适当的统计检验, 以确定两个实验测量变量的显著差异（p≤0.05）。

结果：发情前期Pcm肌纤维CSA高于动情后期, 而Icm肌纤维CSA无变化。卵巢切除增加了Pcm肌纤维CSA, ATD使其加重。EB的补充成功地扭转了卵巢切除诱导的CSA增大。Icm肌纤维CSA无明显变化。

结论：发情周期中波动的卵巢激素水平显著影响Pcm肌纤维的CSA, 而不是Icm。雌激素的作用, 有性腺或外性腺起源, 主要影响Pcm的CSA。

Keywords:

• Aromatase
• estradiol
• estrous cycle
• ovariectomy
• testosterone

Acknowledgements

The authors thank Jesús Ramsés Chávez Ríos and Laura García Rivera for the excellent technical assistance provided.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México [PAPIIT-IA203617] and Consejo Nacional de Ciencia y Tecnología, México [225126].