Insulin regulation of renal glucose metabolism in conscious dogs

Previous studies indicating that postabsorptive renal glucose production is negligible used the net balance technique, which cannot partition simultaneous renal glucose production and glucose uptake. 10 d after surgical placement of sampling catheters in the left renal vein and femoral artery and a nonobstructive infusion catheter in the left renal artery of dogs, systemic and renal glucose and glycerol kinetics were measured with peripheral infusions of [3-³H]glucose and [2-¹⁴C]glycerol. After baseline measurements, animals received a 2-h intrarenal infusion of either insulin (n = 6) or saline (n = 6). Left renal vein insulin concentration increased from 41±8 to 92±23 pmol/l (P < 0.05) in the insulin group, but there was no change in either arterial insulin, (~ 50 pmol/l), glucose concentrations (~ 5.4 mmol/l), or glucose appearance (~ 18 μmol · kg^-1 · min^-1). Left renal glucose uptake increased from 3.1±0.4 to 5.4±1.4 μmol · kg^-1 · min^-1 (P < 0.01) while left renal glucose production decreased from 2.6±0.9 to 0.7±0.5 μmol · kg^-1 · min^-1 (P < 0.01) during insulin infusion. Renal gluconeogenesis from glycerol decreased from 0.23±0.06 to 0.17±0.04 μmol · kg^-1 · min^-1 (P < 0.05) during insulin infusion. These results indicate that renal glucose production and utilization account for ~ 30% of glucose turnover in postabsorptive dogs. Physiological hyperinsulinemia suppresses renal glucose production and stimulates renal glucose uptake by ~ 75%. We conclude that the kidney makes a major contribution to systemic glucose metabolism in the postabsorptive state.