Method for the Study of Metabolite Transfer from Rat Mother to Fetus

Abstract

Infusion medium containing a tracer was introduced through the left uterine artery to 20.5-day pregnant rats. In this way, the left uterine horn received the tracer directly while it reached the right horn after dilution in the mother’s circulation. When U-¹⁴C-D-glucose or U-¹⁴C-L-alanine was infused, radioactivity in fetal blood from the left uterine horn was 3 or 8 times higher respectively than in the right horn and 2 or 6 times higher than in maternal blood. When the infusion was carried out with ¹²⁵I-labelled growth hormone, which is known not to cross the placental barrier, very little radioactivity was found in fetuses compared with that in the mother’s plasma and no differences were observed in blood radioactivity levels of fetuses from either horn. After infusion of U-¹⁴C-D)-glucose through the maternal jugular vein instead of the left uterine artery, radioactivity was the same in fetuses from the left and right horns, indicating that manipulations of the left uterine side did not greatly affect its circulation. These findings, together with the determination of specific radioactivity of the tracer used in both maternal and fetal plasma, validate the technique as a semiquantitative means to determine the direct transfer of any product through the placental barrier in the rat.

Maternal Factors Modulating Nutrient Transfer to Fetus

“…By mea suring the umbilical venous-arterial concen tration differences and the umbilical blood flow, in the conscious chronically catheterized pregnant sheep it has been estimated that the transfer to the fetus is about 17-24pmobkg~l fetal b.w.-min-1 for glucose [4][5][6], S p m o fk g -1 fetal b.w.-min-1 for ala nine [7], and 0.07 pm obkg'1 fetal b.w.-min-1 for glycerol [calculated from 5 and 8]. In the 21-day pregnant rat we have determined the transfer to the fetus of these metabolites by measuring the radioactivity appearing in fe tuses after infusing 14C-labelled ¿¿glucose, L-alanine or glycerol through the uterine ar tery and making proper correction of the data for specific activity dilution of the tracer [9][10][11] transfer values in the rat appear much higher than in the sheep for each of these com pounds. As shown in figure 2, there is an inverse correlation between the transfer of glucose per kilogram of fetus and fetal body weight when values obtained in different transfer species are plotted together ( fig.…”

Relationship Between Maternal and Fetal Fuels and Placental Glucose Transfer in Rats with Maternal Diabetes of Varying Severity

“…To investigate this possibility, in the present study we determined the circulating levels of different metabolic fuels as well as placental glucose transfer by using an in situ placental preparation 15 in STZ-treated, pregnant rats. To learn how the severity of diabetes affects these parameters, STZ-diabetic rats receiving different insulin treatments were also studied.…”

Lactate Production and Absence of Gluconeogenesis from Placental Transferred Substrates in Fetuses from Fed and 48-H Starved Rats

“…Rats were anesthesized with sodium pentobartion was unaffected by maternal starvation. Results show bital(33 mg/kg body weight, intravenous) and operated accordthe significant production by the fetoplacental unit of lac-ing to our previously reported surgical procedure (18). Briefly, a tate transferred maternal substrates and the absence PE-10 cannula (Intramedic) was introduced counter current into of gluconeogenesis in the rat fetus even after 48 h of the left external iliac artery to the beginning of the superior maternal food deprivation.…”

“…No difference in fed and 48-h starved late pregnant rats. Labeled substrates were plasma '4C-glucose between left and right uterine horn infused through the maternal left uterine artery according to our fetuses was observed after maternal infusion with either recently described technique (18) for placental transfer studies [U-14C]-glycerol or [U-14Cj-~-alanine, either in fed or 48-h which allows determination of the metabolic fate of substrates in starved rats. In the mother both [U-14q-glycerol and [U-the rat fetus independently of interconversions occumng in the I4q-L-alanine were efficiently converted to I4C-glucose, mother.…”