Abstract
Previous studies of fetal renal function in animals under surgical stress have produced cinflicting results. Since acute surgical stress may have contributed to some of the previous variability, a chronic sheep preparation has been developed which permtis repeated studies of fetal renal function over several weeks. A hysterotomy was performed during the latter third of pregnancy; catheters were placed in the urinary blader, femoral artery and vein of the fetus, and in the amniiotic sac. Fetal urine was diverted to the outside of the mother for measurements of flow, osmolality and clearance. The glomerular filtration rate (GFR) was studied utilizing inulin 14C administered by a single rapid injection. Following surgery fetal urine osmolality increased by 2-4 times that observed later in pregnancy when a steady state was established. During surgical stress urine flow was frequently less than 0.03 cm3/min/kg body weight and urine osmolality was > 350 mOsm. The urine osmolality stabilized 3-6 days following surgery at a value markedly hypotonic to plasma (range 65-150 mOsm) and fetal urine flow increased to approximately 0.15 cm3/min/kg—over 1,000 cm3/day in a near-term fetus. Fifteen measurements of GFR in two fetuses gave a value of 1.05±0.04 cm3/min/kg (mean ±SEM). Column chromatography on Sephadex G-10 confirmed that there was no hydrolysis of inulin by fetal tissues. Recovery of approximatelyu 85% of inulin 14C in the fetal urine over a 3-day period suggests that the fetal kidney is the primary means of inulin excretion in vitro. The techniques permitting fetal renal function measurements in unstressed animals will be described.
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Gresham, E., Rankin, J., Makowski, E. et al. Fetal Renal Function in Unstressed Pregnancies. Pediatr Res 4, 445–446 (1970). https://doi.org/10.1203/00006450-197009000-00048
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DOI: https://doi.org/10.1203/00006450-197009000-00048