Davison J M, Shiells E A, Philips P R, Lindheimer M D
Medical Research Council (MRC), University of Newcastle, Newcastle upon Tyne, England.
J Clin Invest. 1988 Mar;81(3):798-806. doi: 10.1172/JCI113386.
Serial studies were designed to characterized changes in osmoregulation throughout gestation. Eight women underwent a 2-h infusion of hypertonic saline before conception, during gestational weeks 5-8, 10-12, and 28-33, and then 10-12 wk postpartum. Basal plasma osmolality (Posmol) was already significantly decreased by 5-8 wk (P less than 0.001) and remained 10 mosmol.kg-1 below nonpregnant values throughout pregnancy. The apparent threshold for AVP release (defined as the abscissal intercept of the regression line relating plasma AVP [PAVP] to Posmol) was also decreased significantly throughout gestation, as was the osmotic threshold for thirst (derived from analogue scales relating desire to drink to Posmol). The decrement in osmotic thirst threshold appeared to precede that for AVP release, and consistent with this 24-h urine volumes were significantly greater at 5-8 wk gestation (P less than 0.05). The slopes of each regression equation defining PAVP vs. Posmol (whose r values ranged from 0.79 to 0.99), very reproducible before and after pregnancy, were similar at 5-8 and 10-12 wk, but were markedly reduced in the third trimester (P less than 0.001). These volunteers had randomly undergone an additional infusion before conception (both tests in the luteal phase of the menstrual cycle) when 10,000 IU of human chorionic gonadotrophin (hCG) had been given intramuscularly over a 5-d period. Serum hCG values between 0.2 and 3.3 U.ml-1 were lower than usually seen in pregnancy, but the osmotic thresholds for AVP release and thirst decreased by 3 and 4 mosmol.kg-1, respectively (P less than 0.05). Finally we studied a patient with a molar pregnancy in whom thresholds for hormone release and thirst were both decreased to values resembling normal gestation and remained so for approximately 6 wk postevacuation, only normalizing when hCG had virtually disappeared from her serum. In contrast, thresholds increased within the first two puerperal weeks in two women with normal pregnancies. These data demonstrate (a) osmotic thresholds for both AVP release and thirst decrease within the very first gestational weeks; (b) increment in PAVP per unit increase in Posmol is reduced late in gestation; and (c) hCG may be involved in the osmoregulatory changes of pregnancy.
系列研究旨在明确整个妊娠期渗透压调节的变化情况。8名女性在受孕前、妊娠第5 - 8周、10 - 12周、28 - 33周以及产后10 - 12周接受了2小时的高渗盐水输注。基础血浆渗透压（Posmol）在妊娠5 - 8周时已显著降低（P < 0.001），且在整个孕期一直比非孕期值低10 mosmol·kg⁻¹。血管加压素（AVP）释放的表观阈值（定义为血浆AVP [PAVP]与Posmol关系回归线的横坐标截距）在整个妊娠期也显著降低，口渴的渗透压阈值（由将饮水欲望与Posmol相关的类似量表得出）亦是如此。渗透压口渴阈值的降低似乎先于AVP释放阈值的降低，与此一致的是，妊娠5 - 8周时24小时尿量显著增加（P < 0.05）。定义PAVP与Posmol关系的每个回归方程的斜率（其r值范围为0.79至0.99）在妊娠前后具有很好的可重复性，在5 - 8周和10 - 12周时相似，但在妊娠晚期明显降低（P < 0.001）。这些志愿者在受孕前（月经周期黄体期的两次测试）还随机接受了额外的输注，即在5天内肌肉注射10000 IU人绒毛膜促性腺激素（hCG）。血清hCG值在0.2至3.3 U·ml⁻¹之间，低于孕期通常所见水平，但AVP释放和口渴的渗透压阈值分别降低了3和4 mosmol·kg⁻¹（P < 0.05）。最后，我们研究了一名葡萄胎患者，其激素释放和口渴的阈值均降至类似于正常妊娠的值，并在清宫后约6周内保持如此，仅在血清中hCG几乎消失时才恢复正常。相比之下，两名正常妊娠女性在产后的前两周内阈值升高。这些数据表明：（a）AVP释放和口渴的渗透压阈值在妊娠的最初几周内降低；（b）妊娠晚期每单位Posmol增加时PAVP的增加量减少；（c）hCG可能参与了妊娠的渗透压调节变化。
