Table 3.

Effect of insulin and glucose on the metabolism of 1 mM [U-14C]lactate in isolated renal proximal tubules from nondiabetic lean Zucker rats and ZDF ratsa

Experimental ConditionRatsGlucose Produced[U-14C]Lactate Converted into 14C-GlucosePercentage of Radioactive Glucose Synthesized
1 mM [U-14C]lactateNondiabetic39 ± 154 ± 369 ± 6
Diabetic59 ± 3b73 ± 7b62 ± 3
1 mM [U-14C]lactate + 100 nM insulinNondiabetic38 ± 254 ± 271 ± 5
Diabetic60 ± 4b74 ± 6b62 ± 3
1 mM [U-14C]lactate + 5 mM glucoseNondiabetic55 ± 2
Diabetic75 ± 7b
1 mM [U-14C]lactate + 25 mM glucoseNondiabetic52 ± 3
Diabetic75 ± 7b
  • a Kidney tubules (5.8 ± 0.8 and 8.6 ± 0.4 mg dry wt per flask for nondiabetic and diabetic rats, respectively) were incubated as described in the Materials and Methods section. Results (nmol/mg dry wt per h) are reported as means ± SEM for four experiments with nondiabetic rats and four experiments with diabetic rats. The percentage (means ± SEM) of radioactive glucose synthesized was calculated as half the [U-14C]lactate converted into

  • 14 C-glucose divided by the glucose produced.

  • b P < 0.05 nondiabetic versus diabetic rats, unpaired t test.\