Rates of glucose production and utilization by the foetus in chronically catheterized sheep

Abstract

1. Six well-nourished Scottish Blackface ewes were each prepared at 110-112 days of gestation with indwelling catheters in an umbilical artery and vein and at 2 days before experiment with catheters in each maternal jugular vein. Two-day experiments were conducted between days 124 and 134 of gestation when [2-3H,U-14C]glucose was infused over 9 h into either the maternal or the foetal circulations, separate days being used for each infusion. 2. Plasma glucose specific radioactivities at plateau were used to determine, for a two-pool model representing the glucose system of the mother and foetus, the rates of glucose production, utilization and recycling by the mother and by the foetus and the rates of transfer of glucose between the mother and foetus. 3. The net rate of glucose utilization by the foetus, which we have called the 'foetal glucose requirement', was 7.6 +/- 0.6 mg/min per kg of foetus (n = 8). Compared with the corresponding rate in the mother of 1.1 +/- 0.1 mg/min per kg of mother (n = 8), this indicated a high rate of foetal metabolism. 4. The net rate of foetal uptake of glucose from the mother accounted for only 69 +/- 5% of the foetal glucose requirement, and it has been argued that the remainder was supplied by foetal gluconeogenesis. 5. The rate of glucose recycling within the foetus was high, equal to 108 +/- 16% of the net foetal glucose-utilization rate. The significance of this in terms of either Cori or futile cycling is discussed.

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

“…4], When U -l4C-D-glucosc was infused through the left uterine artery, the percentage of 14C-glucose in the plasma, compared with that in total plasma, was much lower in the fetus from the two horns than in the mother. Although the actual rate of glucose utilization was not measured, these findings indicate that glucose metabolization is faster in the rat fetus than in the mother, in agreement with the conclusion obtained from studies in sheep [9], When infusion was done with Ul4C-L-alaninc, the amount of label found as alanine in the plasma of fetuses from the horn of the same infusion site was much greater than that found as glucose when the infusion was done with U -l4C-D-glucose. This difference may be interpreted as a con sequence of the faster conversion of glucose into other metabolites.…”

Substrate Metabolism and Interrelationships in the Ovine Fetus in Utero

“…1980 (Grassl 1974 Rescigno and Gurpide (1973 (Fig. 4) Warnes et al (1911a) using single injection techniques and to recent estimates from continuous infusion studies (Anand et al 1979;' Hodgson et al 1980;Prior 1980 (Tsoulos et al 19711' Schreiner et al 1978).…”

“…Warnes et al (1917a) injected labelled substrates into the fetal circulation and determined kinetic parameters from the disappearance of the label from the circulation. Others infused labelled substrates continuously into the fetal circulation and estimated substrate utilization and interconversion from the plateau specific activity (Hodgson et al 1980;Prior 1980;Anand et al 1979Anand et al . 1980 (Grassl 1974 Rescigno and Gurpide (1973 (Fig.…”

Tyrosine Turnover and Oxidation in the Ovine Fetus in Utero

“…1) (Shipley and Clark 1972). This approach to fetal metabolism and its experimental validity have been recently described in detail with reference to glucose metabolism (Hodgson et al 1980 (Meier et al . 1981;Kitts and Krishnamurti 1982b).…”

“…A two-compartment model was employed ( Fig. 1) to depict the maternal-fetal exchange of tyrosine using the terminology of Hodgson et al (1980). The fetal body weight in utero was estimated from birth weight using the regression equation of Gresham et al (79'72).…”