DDAVP-induced maternal hyposmolality increases ovine fetal urine flow.
Fetal urine flow is influenced by fetal intravascular volume, glomerular filtration rate, tubular reabsorption, and fluid regulatory hormones. As maternal-to-fetal fluid transfer is dependent on hydrostatic and osmotic gradients, we postulated that a chronic decrease in maternal plasma osmolality would promote transplacental fluid transfer and increase fetal urine flow. Six pregnant ewes and singleton fetuses (131 +/- 2 days; term = 150 days) received bladder and hindlimb arterial and venous catheters. After 5 days, plasma and urine composition, urine flow rate (Uvol), and plasma arginine vasopressin (AVP) levels were measured during a 2-h control period. At 2 h, tap water (2 liter, 38 degrees C) was administered to the ewe. At 3 h, ewes received a 20-micrograms bolus of 1-desamino-[D-Arg8]vasopressin (DDAVP), followed by continuous infusion (4 micrograms/h). In response to water loading, maternal urine osmolality decreased (761 +/- 158 to 339 +/- 13 mosmol/kgH2O), and Uvol increased. After DDAVP, maternal urine osmolality increased (1,270 +/- 89 mosmol/kgH2O), and Uvol, hematocrit, plasma osmolality (304 +/- 1 to 284 +/- 4 mosmol/kgH2O), and protein concentration decreased. Five hours after maternal DDAVP infusion, fetal plasma osmolality decreased (300 +/- 1 to 281 +/- 3 mosmol/kgH2O), and Uvol increased (0.4 +/- 0.1 to 1.3 +/- 0.2 ml/min) and remained elevated at 24 h. There was no change in fetal plasma DDAVP (immunoreactive AVP) levels or fetal urine osmolality. Controlled changes in maternal plasma osmolality may prove useful in modulating fetal urine flow and, ultimately, amniotic fluid volume.
Nijland
M J
MJ
Department of Obstetrics and Gynecology, University of California Los Angeles School of Medicine, Harbor-UCLA Medical Center, Torrance 90502.
Ross
M G
MG
Kullama
L K
LK
Bradley
K
K
Ervin
M G
MG
D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology*; D004231:Diuresis / Q000187:drug effects*; D005260:Female; D005312:Fetal Blood / Q000187:drug effects; D005333:Fetus / Q000187:drug effects / Q000502:physiology*; D007668:Kidney / Q000187:drug effects / Q000196:embryology; D008431:Maternal-Fetal Exchange; D009994:Osmolar Concentration; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood / Q000378:metabolism* / Q000502:physiology; D012756:Sheep
D001127:Arginine Vasopressin; D003894:Deamino Arginine Vasopressin