Contributions by kidney and liver to glucose production in the postabsorptive state and after 60 h of fasting

Contributions of renal glucose production to whole-body glucose turnover we re determined in healthy individuals by using the arteriovenous balance tec hnique across the kidneys and the splanchnic area combined with intravenous infusion of [U-C-13(6)]glucose, [3-H-3]glucose, or [6-H-3]glucose. In the postabsorptive state, the rate of glucose appearance was 11.5 +/- 0.6 mu mo l.kg(-1).min(-1) Hepatic glucose production, calculated as the sum of net g lucose output (9.8 +/- 0.8 mu mol.kg(-1).min(-1)) and splanchnic glucose up take (2.2 +/- 0.3 mu mol.kg(-1).min(-1)) accounted for the entire rate of g lucose appearance. There was no net exchange of glucose across the kidney a nd no significant renal extraction of labeled glucose, The renal contributi on to total glucose production calculated from the arterial, hepatic, and r enal venous C-13-enrichments (glucose M+6) was 5 +/- 2%. In the 60-h fasted state, the rate of glucose appearance was 8.2 +/- 0.3 mu mol.kg(-1).min(-1 ). Hepatic glucose production, estimated as net splanchnic output; (5.8 +/- 0.7 mu mol.kg(-1).min(-1)) plus splanchnic uptake (0.6 +/- 0.8 mu mol.kg(- 1).min(-1)) accounted for 79% of the rate of glucose appearance, There was a significant net renal output of glucose (0.9 +/- 0.3 mu mol.kg(-1).min(-1 )), but; no significant extraction of labeled glucose across the kidney. Th e renal contribution to whole-body glucose turnover calculated from the C-1 3-enrichments was 24 +/- 3%. We concluded that 1) glucose production by the human kidney in the postabsorptive state, in contrast to recent; reports, makes at most only a minor contribution (similar to 5%) to blood glucose ho meostasis, but that 2) after 60-h. of fasting, renal glucose production may account for 20-25% of whole-body glucose turnover.