Lapolt P S, Matt D W, Judd H L, Lu J K
Biol Reprod. 1986 Dec;35(5):1131-9. doi: 10.1095/biolreprod35.5.1131.
In multiparous rats, the incidence of regular estrous cyclicity and fertility decreases markedly at middle age. However, recent studies have shown that repeated pregnancies or progesterone (P) implants can subsequently cause retired breeder females to maintain regular cyclicity for an extended period of time; these results suggest a P-mediated deceleration of reproductive aging. In the present study, we examined the relation of ovarian steroid levels in young virgin females to their subsequent estrous cyclicity and reproductive function during aging as compared to multiparous females. Beginning at 4 mo of age and continuing to 6 mo of age, regularly cyclic virgin rats received either consecutive P implants (n = 41) or no implants (controls, n = 45) for 3 wk, followed by implant removal for 1 wk. Additional females (n = 72) were mated and allowed to undergo repeated pregnancies at 4, 6 1/2, and 8 mo of age. Blood samples were obtained throughout the estrous cycle (virgin females), during pregnancy (multiparous rats), and on Day 11 of successive treatments with P implants (virgins with P implants) for P, estradiol (E2), and testosterone (T) measurements. Subsequently, regularly cyclic females from all three groups were mated with fertile males to undergo term pregnancies at 10 and 12 mo of age. While the virgin controls showed cyclic increases in P, T, and E2 secretion during their estrous cycles, the P-implanted females had persistently low E2 and high P and T levels during treatment, which indicates an inhibition of ovarian E2 synthesis by P.(ABSTRACT TRUNCATED AT 250 WORDS)
在经产大鼠中，正常发情周期和生育能力的发生率在中年时会显著下降。然而，最近的研究表明，反复怀孕或植入孕酮（P）随后可使退役繁殖雌鼠在较长时间内维持正常周期；这些结果提示P介导了生殖衰老的减速。在本研究中，我们比较了年轻未孕雌鼠与经产雌鼠卵巢类固醇水平与它们随后在衰老过程中的发情周期和生殖功能之间的关系。从4月龄开始持续到6月龄，规律发情的未孕大鼠连续3周接受P植入（n = 41）或不植入（对照组，n = 45），随后移除植入物1周。另外的雌鼠（n = 72）在4、6.5和8月龄时交配并经历反复怀孕。在整个发情周期（未孕雌鼠）、孕期（经产大鼠）以及连续接受P植入治疗的第11天（接受P植入的未孕雌鼠）采集血样，以检测P、雌二醇（E2）和睾酮（T）。随后，将来自所有三组的规律发情雌鼠与可育雄鼠交配，在10和12月龄时进行足月妊娠。未孕对照组在发情周期中P、T和E2分泌呈周期性增加，而接受P植入的雌鼠在治疗期间E2持续处于低水平，P和T水平较高，这表明P抑制了卵巢E2的合成。（摘要截短于250词）
