RESPIRATION OF AMNIOTIC-FLUID IN NEAR-TERM FETAL RABBIT

Objective: To examine the existence of amniotic fluid inhalation in fo etal rabbit near term. Study design: Rabbit red cells labelled with 51 radio-chromium (Cr51-S1: Injectable solution sodium chromate, volumic activity: 74 MBq/ml; Cis-BioInternational, France) were injected into the amniotic sac of 24 New Zealand White foetal rabbits (mean gestati on: 31 days) at day 25 per-laparotomy. At day 26, just prior to caesar ean section, human serum albumine labelled with 125 radio-active iode (125I-HSA) (SERALB-125: human serum albumin labelled with radioactive Iode 125, volumic activity: 185 kBq/ml, Cis-BioInternational, France) was injected into each amniotic sac. The lungs, digestive tracts, kidn eys and liver were excised separately and radioactivity counted in eac h organ. Results: On day 26 of gestation, the 51Cr-RC radioactivity ra te per gram of tissue in lungs, digestive tract amniotic fluid, liver and kidneys were respectively 1.66 +/- 2.8%, 1.15 +/- 1.6%, 0.015 +/- 0.02% and 0.04 +/- 0.07% of the total amount of radioactivity injected into the amniotic sac at day 25. The lungs' radioactivity was signifi cantly higher than liver (t = 2.94, P < 0.01) or kidneys radioactivity (t = 2.38, P < 0.05). The 125I-HSA injected just prior to caesarean s ection at day 26 was not found in any foetal organ. Conclusions: Lung radioactivity is not related to gasps induced by caesarean section, or to a vascular diffusion since lung radioactivity was significantly hi gher than liver or kidneys' radioactivity. The results of these series of experiments demonstrate that amniotic fluid inhalation does exist in foetal rabbit near term.