TABLE 5

Protein turnover during insulin infusion (plasma insulin level 44 ± 3 μU/ml in CF patients and 45 ± 2 μU/ml in control subjects)

Control subjectsCF patients
Indexes of protein breakdown
Amino acid flux (μmol · kg FFM–1 · h–1)
 [13C]KIC110 ± 6*128 ± 5
 [13C]Leucine88 ± 5*95 ± 5
 [2H4]Tyrosine43 ± 2*51 ± 4
 [15N]Phenylalanine50 ± 252 ± 4
Index of protein synthesis
Phenylalanine disappearance not accounted for by conversion to tyrosine (μmol · kg FFM–1 · h–1)
 [15N]Phenylalanine46 ± 344 ± 4
Index of amino acid catabolism
Phenylalanine conversion to tyrosine (μmol · kg FFM–1 · h–1)5 ± 0*6 ± 1
  • Data are means ± SE.

  • * P < 0.05 compared with day 1;

  • P < 0.05 control subjects vs. CF patients;

  • Synthesis and oxidation were not calculated from the leucine or KIC data because glucose was infused during the insulin infusion, which results in contamination from exogenous [13C]leucine.