Table 2.
Kinetic constants of HDL-analyte uptake by various cell types
Kinetic constants ± S.E. were calculated from the fit of the dose-response curves in Fig. 3 to a two-parameter hyperbolic function, i.e., y = ax/(b + x), where x is HDL protein concentration, y is the radiolabel uptake, a is the maximum uptake (Vmax), and b is Km, the HDL-protein concentration at 50% of Vmax; catalytic efficiency (E) = (Vmax/ Km).
| Cell type | HDL analyte | Vmax | Km | Vmax/Km |
|---|---|---|---|---|
| nmol/mg cell protein | μg HDL-protein/ ml | |||
| CHO K1 | HDL-[3H]CE | 7,740 ± 3,500 | 127 ± 91 | 60.70 |
| HDL-[125I]apoAI | 97 ± 51 | 99 ± 89 | 0.98 | |
| HDL-[125I]apoAII | 38 ± 19 | 40 ± 45 | 0.94 | |
| CHO ldlA7 | HDL- [3H]CE | 4,900 ± 780 | 59 ± 19 | 82.70 |
| HDL-[125I]apoAI | 41 ± 9 | 68 ± 28 | 0.60 | |
| HDL-[125I]apoAII | 43 ± 25 | 90 ± 91 | 0.48 | |
| CHO SR-B1 | HDL- [3H]CE | 32,800 ± 4,800 | 37 ± 13 | 882.00 |
| HDL-[125I]apoAI | 93 ± 27 | 48 ± 31 | 1.92 | |
| HDL-[125I]apoAII | 25 ± 2 | 60 ± 10 | 0.42 | |
| Huh7 | HDL- [3H]CE | 9,730 ± 1,750 | 84 ± 27 | 116.00 |
| HDL-[125I]apoAI | 15 ± 2 | 38 ± 14 | 0.41 | |
| HDL-[125I]apoAII | 7.6 ± 0.9 | 32 ± 9 | 0.24 |