van der Schoot P, Lankhorst R R, de Roo J A, de Greef W J
Endocrinology. 1978 Sep;103(3):949-56. doi: 10.1210/endo-103-3-949.
Lactation pseudopregnancy in rats suckling a 5-pup litter lasted 22.0 +/- 0.4 days (mean +/- SEM; n = 11). By day 13 of lactation (day 1 of lactation = day of parturition), the continuation of lactation pseudopregnancy was dependent on the suckling stimulus, as litter removal on day 13 resulted consistently in ovulation on day 16. Measurements of various hormones before and after litter removal revealed high concentrations of progesterone and PRL during lactation and a rapid drop of both hormone concentrations after litter removal. Lactation pseudopregnancy in rats suckling a 10-pup litter lasted 26.1 +/- 0.9 days (n = 16). After litter removal on day 13 of lactation, the lactation pseudopregnancy continued for a further 7- to 11-day period, as evidenced by daily vaginal smears which remained mucified during that period. Measurements of hormone concentrations revealed continuously high concentrations of PRL before litter removal and a pattern of PRL secretion characterized by at least two diurnal peaks during the first days after litter removal. Progesterone concentrations decreased by 50% after litter removal, but the levels then remained constant and well above those found after the removal of 5-pup litters. It is argued that the different response to litter removal on day 13 of lactation between rats suckling 5 or 10 pups is due to the initiation of PRL peaks in rats with 10-pup litters: these PRL peaks are able to maintain luteal function for some period. It is further argued that the initiation of PRL peaks in rats with 10-pup litters is due to the high blood concentrations of progesterone at the time of litter removal compared to those of rats with a 5-pup litter.
哺乳 5 只幼崽的大鼠的泌乳假孕持续 22.0±0.4 天（平均值±标准误；n = 11）。到泌乳第 13 天（泌乳第 1 天 = 分娩日），泌乳假孕的持续取决于哺乳刺激，因为在第 13 天移除幼崽会导致在第 16 天一致排卵。移除幼崽前后各种激素的测量显示，泌乳期间孕酮和催乳素浓度较高，移除幼崽后两种激素浓度迅速下降。哺乳 10 只幼崽的大鼠的泌乳假孕持续 26.1±0.9 天（n = 16）。在泌乳第 13 天移除幼崽后，泌乳假孕又持续了 7 至 11 天，每日阴道涂片显示在此期间仍为黏液状，这证明了这一点。激素浓度测量显示，移除幼崽前催乳素浓度持续较高，移除幼崽后的头几天催乳素分泌模式至少有两个昼夜高峰。移除幼崽后孕酮浓度下降了 50%，但随后水平保持恒定且远高于移除 5 只幼崽的大鼠。有人认为，哺乳 5 只或 10 只幼崽的大鼠在泌乳第 13 天对移除幼崽的不同反应是由于哺乳 10 只幼崽的大鼠中催乳素高峰的开始：这些催乳素高峰能够在一段时间内维持黄体功能。进一步有人认为，哺乳 10 只幼崽的大鼠中催乳素高峰的开始是由于移除幼崽时孕酮的血浓度高于哺乳 5 只幼崽的大鼠。
