TABLE 1

Similarities of kinetic and pharmacological characteristics of liver, pancreatic islets, pituitary, AtT20 cells, and GLUTag cells

TissuenVmax(nmol · mg tissue−1 · h−1)
Glucose S0.5(mmol/l)
nH
% recovery
Relative activity (islet glucokinase = 1)
Basal+GKABasal+GKABasal+GKABasal+GKABasal+GKA
Mouse liver5215 ± 23.5283 ± 31.59.64 ± 0.891.35 ± 0.091.57 ± 0.031.14 ± 0.0296.0 ± 0.6199.0 ± 1.709.9212.1
Freshly isolated rat islets921.7 ± 2.2223.4 ± 1.768.10 ± 0.800.93 ± 0.091.38 ± 0.061.41 ± 0.1888.9 ± 4.4988.9 ± 2.3511
Pituitary (rat)53.30 ± 0.184.90 ± 0.268.93 ± 2.011.48 ± 0.351.44 ± 0.090.98 ± 0.0681.0 ± 8.8180.8 ± 2.630.150.21
Pituitary (mouse)*24.09 ± 0.094.62 ± 0.097.98 ± 0.031.52 ± 0.231.86 ± 0.151.34 ± 0.0897 ± 1.41124 ± 240.190.2
AtT-20 cells80.8 ± 0.071.1 ± 0.087.78 ± 0.330.85 ± 0.061.72 ± 0.111.04 ± 0.040.040.05
GLUTag cells965.9 ± 3474.5 ± 40.18.8 ± 3.51.5 ± 0.51.4 ± 0.51.3 ± 0.53.043.18
  • Data are n ± SE, unless otherwise indicated.

  • *

    * Five mouse pituitaries were pooled for each of the two analyses. Results were obtained by assays conducted in the absence of GKAs and also with near-saturating 30 μmol/l of a GKA. Note that all Vmax values are expressed in terms of nanomole of product generated per milligram of tissue per hour. This uniformity of expression was achieved by using an interconversion factor of 7.0 in cases where protein measurements rather than tissue weights were available. Recovery was calculated by distributing loss equally between tissue sample and recombinant glucokinase standard.