Metabolic responses of the kidney in fetal sheep: effect of acute and spontaneous hypoxemia. 
To examine the effects of hypoxemia on carbohydrate and O2 consumption by the fetal kidney, we inserted catheters into the descending aorta, inferior vena cava, and left renal vein of 14 fetal sheep at 120-130 days gestation.  Three to nine days after surgery, nine fetuses had an arterial PO2 of 22 +/- 2 mmHg and O2 content of 2.68 +/- 0.65 mM. In these fetuses, the kidneys consumed O2 (107 +/- 21 mumol X min-1 X 100 g-1, mean +/- SD) and lactate (14 +/- 9.6 mumol X min-1 X 100 g-1) but produced glucose (5.6 +/- 6.5 mumol X min-1 X 100 g-1; 95% confidence limits, 0.62 and 10.5).  When acute hypoxemia was induced by decreasing maternal fractional inspired O2 (FIO2) to 0.09, renal O2 consumption fell slightly (to 82 +/- 21 mumol X min-1 X 100 g-1), and there was net glucose uptake and net lactate release.  A group of five fetuses was spontaneously hypoxemic 3-5 days after surgery and had an arterial PO2 of 14 +/- 2 mmHg and O2 content of 1.99 +/- 0.51 mM. Renal blood flow and O2 consumption were greater in these fetuses than in the normoxemic fetuses.  There was net lactate uptake and no net flux of glucose across the renal circulation.  These results demonstrate that renal metabolism of carbohydrate is altered by changes in fetal oxygenation.