Matousek M, Carati C, Gannon B, Brännström M
Department of Obstetrics and Gynaecology, Göteborg University, Göteborg, Sweden.
Reproduction. 2001 Feb;121(2):307-14. doi: 10.1530/rep.0.1210307.
The ovulatory process in the rat comprises a period of about 12-15 h, from the time of the preovulatory LH surge to follicular rupture and extrusion of the oocyte. Follicular rupture is most likely caused, at least in part, by decreased tensile strength at the follicular apex due to degradation of collagen fibres of the extracellular matrix. It has been debated whether changes in intrafollicular pressure occur during the ovulatory process and whether such changes facilitate rupture of the follicle. In the present study, rats were primed with equine chorionic gonadotrophin (eCG, 10 iu) followed by hCG (10 iu) 48 h later. The intrafollicular pressure in the preovulatory follicle was recorded during 1 h at distinct time phases of the ovulatory process by use of an active servo-null pressure system based on the proportionality between electrical resistance and pressure within the tip of an inserted micropipette. The basal intrafollicular pressure was 16.6 +/- 1.0 mm Hg at the preovulatory phase (48 h after eCG) and increased gradually throughout the ovulatory process to 21.4 +/- 2.4 mm Hg at 4-7 h after hCG (mid-ovulatory phase) and 23.9 +/- 1.9 mm Hg at 8-12 h after hCG (late ovulatory phase; significantly higher (P < 0.01) than the preovulatory phase). Short-term peaks of increased pressure, possibly representing contractility, were not detected in follicles of the preovulatory phase, but were seen in most follicles of the mid- and late ovulatory phases. The mean amplitude of the short-term pressure increases was 12.3 +/- 3.2 mm Hg and the increases occurred at intervals of 24.7 +/- 3.6 s. These short-term increments in intrafollicular pressure were still present after hysterectomy had been performed. The wall tension index was calculated by measuring the follicular size and estimating the thickness of the follicle wall. The index increased from 93.9 +/- 13.3 at the preovulatory phase to 207.3 +/- 47.7 (mid-ovulatory phase) and to significantly higher values at the late ovulatory phase (320.9 +/- 33.5). In conclusion, this study shows that there is an increase in intrafollicular pressure in the ovulating follicle of the rat ovary during the late stages of the ovulatory process, and that short-term increases in intrafollicular pressure occur during the late phase of the ovulatory process. These changes in pressure may be essential for follicular rupture to proceed normally.
大鼠的排卵过程约持续12 - 15小时，从排卵前促黄体生成素（LH）峰出现之时起，直至卵泡破裂并排出卵母细胞。卵泡破裂很可能至少部分是由于细胞外基质胶原纤维降解导致卵泡顶端抗张强度降低所致。关于在排卵过程中卵泡内压力是否发生变化以及这种变化是否有助于卵泡破裂，一直存在争议。在本研究中，给大鼠注射马绒毛膜促性腺激素（eCG，10国际单位）进行预处理，48小时后再注射人绒毛膜促性腺激素（hCG，10国际单位）。利用基于插入的微量移液器尖端内电阻与压力成正比的有源伺服零压力系统，在排卵过程的不同时间阶段记录排卵前卵泡内的压力1小时。排卵前期（eCG注射后48小时）卵泡内基础压力为16.6±1.0毫米汞柱，在整个排卵过程中逐渐升高，在hCG注射后4 - 7小时（排卵中期）升至21.4±2.4毫米汞柱，在hCG注射后8 - 12小时（排卵后期）升至23.9±1.9毫米汞柱（显著高于排卵前期，P < 0.01）。在排卵前期卵泡中未检测到压力升高的短期峰值（可能代表收缩性），但在排卵中期和后期的大多数卵泡中可见。短期压力升高的平均幅度为12.3±3.2毫米汞柱，升高间隔为24.7±3.6秒。子宫切除术后，卵泡内压力的这些短期升高仍然存在。通过测量卵泡大小并估计卵泡壁厚度来计算壁张力指数。该指数从排卵前期的93.9±13.3增加到排卵中期的207.3±47.7，并在排卵后期显著升高（320.9±33.5）。总之，本研究表明，在排卵过程后期，大鼠卵巢排卵卵泡内的卵泡内压力升高，并且在排卵过程后期卵泡内压力会出现短期升高。这些压力变化可能对卵泡正常破裂至关重要。
