AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 4 781-R786, Copyright © 1986 by American Physiological Society
Fate of labeled albumin and erythrocytes following injection into amniotic cavity of sheep
S. Tomoda, R. A. Brace and L. D. Longo
We have previously described a method to measure the amniotic fluid (AF)
volume and fetal swallowing rate in near-term sheep by use of 125I-labeled
albumin (RISA) and 51Cr-labeled red blood cells (51Cr-RBC). However, when
we measured these volumes on consecutive days, reentry of the radionuclides
into the amniotic cavity from fetal urine affected the calculated values of
AF volume and swallowing rates. In an attempt to clarify the recirculation
problem, we injected RISA and Cr-RBC daily for 9 days into the AF of five
chronically catheterized pregnant sheep (124 days gestation on the 1st
experimental day). We calculated AF volume and fetal swallowing rate,
comparing those values to the values corrected for fetal urine isotopic
counts. The mean AF volume and fetal swallowing rate measured by RISA were
808 +/- 48 ml (mean +/- SE) and 559 +/- 29 ml/day, respectively. These
values were only slightly different from the corrected volumes, 808 +/- 48
ml and 561 +/- 29 ml/day, respectively, because fetal urine 125I activity
reached only 4.8% of AF activity even on the 9th day. In contrast,
51Cr-activity in fetal urine on the 9th day showed 47% of the activity of
AF. The mean uncorrected AF volume (785 +/- 44 ml) and swallowing rate (561
+/- 31 ml/day) measured by Cr-RBC were different from the corrected values
(790 ml and 570 ml/day, respectively). After the 4th day these differences
were particularly conspicuous.(ABSTRACT TRUNCATED AT 250 WORDS)
