VOLUME AND GLUCOSE-CONCENTRATION OF RAT AMNIOTIC-FLUID - EFFECTS ON EMBRYO NUTRITION AND AXIS ROTATION

In order to pursue our previous studies of the changes in neural tube microvilli produced by glucose, we developed a micro method of measuri ng glucose concentration in the very small volumes of amniotic fluid d uring neurulation. The volume of amniotic fluid was found to increase nearly 10-fold during major neurulation (day 10 to day 11 in the rat). This increase in volume and our repeated observations that physical r emoval of the restraining amnion initiates embryonic rotation leads us to propose that the growth of the amniotic cavity is essential for co nversion from the ventral-to dorsi-flexion of the embryonic axis. Amni otic fluid volume continues to increase until day 18 but dropped by da y 20. A method for glucose determination was developed using the color reaction on glucose oxidase indicator paper. The intensity of the col or was analyzed with a color scanner. Amniotic glucose was 27.1 +/- 1. 6 mg/dl on day 10 and continued in this range with some fluctuation un til day 20 when it decreased. We isolated days 10, 11, and 16 embryoni c sites from their decidua and incubated them at 0 degrees C and 38 de grees C while measuring glucose concentration. The glucose concentrati on did not show significant decrease at 0 degrees C on day 10 or 11 or on day 16 at 38 degrees C. At 38 degrees C the day 10 embryo amniotic fluid glucose disappeared after 22 minutes and the day 11 amniotic fl uid glucose was gone in 34 minutes. These depletion times were statist ically different. The magnitude of glucose depletion on day 10 was sho wn by calculation to be approximately 323 mu moles/gm protein per hour which is a substantial portion of the glucose utilized by the embryo as determined in previous experiments (731 mu moles/gm protein per hou r). This model may serve as a way to study glucose utilization by embr yos after their exposure to various teratogens. (C) 1994 Wiley-Liss, I nc.