title: Fetal renal contribution to amniotic fluid osmolality during maternal hypertonicity.
abstract: The contribution of fetal urine to the increase in amniotic fluid osmolality during maternal hypertonicity was studied in chronically catheterized sheep of 130-135 days gestation. Nine percent NaCl was injected simultaneously into fetal and maternal veins, followed by a continuous infusion into the maternal vein. Maternal and fetal plasma osmolalities rose by 15 +/- 1 (SE) and 13 +/- 1 mosmol/kg, respectively, and remained constant for 4 h. Fetal urine osmolality rose significantly from 188 +/- 31 to 277 +/- 32 mosmol/kg within 1 h and remained constant thereafter. Fetal urine flow rose transiently, fell to normal within 10 min, and averaged 70% of normal beyond 1 h. Amniotic fluid osmolality rose by 10.8 +/- 2.8 mosmol/kg over 4 h. Following hypertonic injection into three fetuses blocked by the arginine vasopressin antagonist d(CH2)5D-tyr(Et)VAVP, urine osmolality did not change, and amniotic fluid osmolality rose by 2.7 +/- 0.3 mosmol/kg. Thus it appears that the increase in amniotic fluid osmolality during maternal hypertonicity may be due largely to an increased fetal urine osmolality coupled with a decreased flow of fetal urine into the amniotic space, rather than to bulk flow of fluid across the membranes and uterine wall.
mesh_terms: D000653:Amniotic Fluid / Q000032:analysis*; D000818:Animals; D001127:Arginine Vasopressin / Q000037:antagonists & inhibitors; D005260:Female; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000196:embryology*; D008431:Maternal-Fetal Exchange; D009994:Osmolar Concentration; D011247:Pregnancy; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D012756:Sheep; D012965:Sodium Chloride / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D012462:Saline Solution, Hypertonic; D001127:Arginine Vasopressin; D012965:Sodium Chloride