Baerwolff M, Bie P
Department of Medical Physiology C, Panum Institute, University of Copenhagen, Denmark.
Am J Physiol. 1988 Dec;255(6 Pt 2):R940-5. doi: 10.1152/ajpregu.1988.255.6.R940.
The possibility that small amounts of vasopressin (AVP) reduce water excretion without affecting solute excretion was investigated in conscious dogs. AVP was infused intravenously for 120 min at rates of 2 and 5 pg.min-1.kg body wt-1 during water diuresis elicited by a sustained water load of 2% body wt. During control experiments urine osmolality was constantly approximately 60 mosmol/kgH2O; during AVP infusions it increased by factors of 1.36 (P less than 0.01) and 2.12 (P less than 0.01), respectively, concomitant with 39 +/- 6 and 61 +/- 7% reductions in urine flow. Osmolar and free water clearances decreased significantly. Sodium excretion did not change; changes in potassium excretion during AVP were similar to those of the control series, i.e., a gradual decline. During AVP, 5 pg.min-1. kg-1, creatinine and urea clearances decreased (25 +/- 2 and 31 +/- 7%, respectively, both P less than 0.01). With the assumption of metabolic clearance rates of AVP of 15-40 ml.min-1.kg body wt-1, the increase in plasma AVP during the infusion of 2 pg.min-1.kg body wt-1 was 5-13 X 10(-14) M. It is concluded that small increments in plasma AVP may reduce glomerular filtration rate and that with increasing levels of AVP in plasma 1) reduction of free water clearance, 2) reduction in urea clearance, and 3) natriuresis-kaliuresis occur in that order. Apparently AVP cannot reduce water excretion without changing the rate of excretion of solutes.
在清醒犬中研究了小剂量血管加压素（AVP）减少水排泄而不影响溶质排泄的可能性。在给予2%体重的持续水负荷引发水利尿期间，以2和5 pg·min⁻¹·kg体重⁻¹的速率静脉输注AVP 120分钟。在对照实验期间，尿渗透压恒定约为60 mosmol/kgH₂O；在输注AVP期间，尿渗透压分别增加了1.36倍（P<0.01）和2.12倍（P<0.01），同时尿流量分别减少了39±6%和61±7%。渗透清除率和自由水清除率显著降低。钠排泄没有变化；AVP输注期间钾排泄的变化与对照系列相似，即逐渐下降。在AVP 5 pg·min⁻¹·kg⁻¹输注期间，肌酐清除率和尿素清除率下降（分别为25±2%和31±7%，P均<0.01）。假设AVP的代谢清除率为15 - 40 ml·min⁻¹·kg体重⁻¹，在输注2 pg·min⁻¹·kg体重⁻¹期间血浆AVP的增加量为5 - 13×10⁻¹⁴ M。结论是血浆AVP的小幅增加可能降低肾小球滤过率，并且随着血浆AVP水平的升高，1）自由水清除率降低，2）尿素清除率降低，3）钠利尿 - 钾利尿按此顺序发生。显然，AVP在不改变溶质排泄率的情况下不能减少水排泄。
