Artificial perfusion of the fetal circulation of the in situ mouse placenta: Methodology and validation

K Here we present methodology and validation (including measurement of unidirectional maternofetal clearance (Kmf) of Ca-45 and C-14-mannitol) for in situ perfusion of the mouse placenta. On day 18 of gestation (term = 19 days) mice were anaesthctised and the uterus delivered into a saline bath (40 degrees C). A fetus was selected, the umbilical artery and vein catheterised and perfused with Krebs Ringer (pH 7.4) at 60 mu l/min. Ca-45/C-14-mannitol (2 mu Ci/5 mu Ci in 50 mu l saline) was injected via maternal tall vein. Perfusate samples Were collected every 5 min for 45 min. Maternal carotid artery pressure was monitored throughout perfusion. A terminal maternal cardiac blood sample was taken and analysed. Placentas were immersion fixed and processed for electron microscopy. Kmf for Ca-45 and C-14-mannitol was calculated as perfusate [Ca-45 or C-14-mannitol] x perfusion rate/maternal plasma [Ca-45 or C-14-mannitol] x placental weight. Maternal cardiac blood chemistry at termination (n = 8-15, mean +/- SEM) was as follows: pH 7.153 +/- 0.016, PCO, 45.48 +/- 2.06 mmHg, PO2 66.47 +/- 7.10 mmHg, Na+ 151.4 +/- 1.2 mmol/l, K+ 5.54 +/- 0.17 mmol/l, Ca2+ 1.15 +/- 0.03 mmol/l, glucose 7.2 +/- 0.5 mmol/l, and lactate 1.76 +/- 0.77 mmol/l. A successful 45 min perfusion in which perfusate recovery was > 95% occurred in > 50% of animals. Perfusion did not alter placental morphology or carotid pressure. Kmf (mu l/min/g placenta) for Ca-45 (66.0 +/- 8.4 (n = 7)) was significantly higher than Knif for C-14-mannitol (20.0 +/- 2.4 (n = 5)) (P < 0.01). These data demonstrate physiological perfusion of the mouse placenta in Situ and its usefulness for measurement of solute transfer.