Parameters | Description | Periportal | Perivenous |
---|---|---|---|
V 4-a | Maximum uptake velocity for E1S (nmol/min/106cells) | 2.9 | 2.9 |
K | Michaelis-Menten constant for E1S uptake (μM) | 11.8 ± 0.9 | 10.3 ± 4.1 |
P 4-a | Bidirectional uptake clearance for E1S (μl/min/106cells) | 4.0 | 4.0 |
P | Bidirectional uptake clearance for E1 (μl/min/106cells) | 1484 ± 242 | 1463 ± 149 |
V 4-b | Maximum desulfation rate for E1S (nmol/min/106cells) | 2.2 | 1.9 |
K 4-b | Michaelis-Menten constant for desulfation of E1S (μM) | 30.4 | 34.8 |
V | Maximum sulfation rate for E1 (nmol/min/106cells) | 0.014 ± 0.015 | 0.077 ± 0.0524-150 |
K 4-c | Michaelis-Menten constant for sulfation of E1 (μM) | 4.4 | 5.9 |
V 4-d | Maximum metabolism rate for E1 (nmol/min/106cells) | 5.9 ± 2.0 | 9.4 ± 2.44-150 |
K 4-d | Michaelis-Menten constant for metabolism of E1 to M (μM) | 18 ± 3.0 | 19 ± 0.6 |
CL | Excretion of E1S to intracellular vesicle (μl/min/106cells) | 0.66 ± 0.25 | 0.49 ± 0.23 |
nE1S4-e | Number of binding sites for E1S | 1.5 | 1.5 |
k | Binding association rate constant for E1S (l/min/μM/106cells) | 0.0014 ± 0.0001 | 0.0020 ± 0.0009 |
k 4-f | Binding dissociation rate constant for E1S (l/min/106cells) | 0.033 | 0.046 |
f | Unbound fraction of intracellular E1 | 0.030 ± 0.005 | 0.025 ± 0.004 |
f 4-g | Unbound fraction of extracellular E1 | 0.84 | 0.84 |
Vc 4-h | Cellular volume (ml/106 cells) | 0.0036 | 0.0041 |
Vec | Extracellular volume (ml/106cells) | 0.9964 | 0.9959 |
Fitted values were obtained for each set of experiments, and data were expressed as mean ± SD; n = 5.
↵4-150 Statistically different from parameter for periportal hepatocytes (ANOVA, P < 0.05).
↵4-a Obtained from Tan et al. (1999) and scaled up as described under Experimental Procedures.
↵4-b Scaled up from the desulfation rate constants for E1S, obtained from S9 of zonal hepatocytes.
↵4-c Constrained as V /CL .
↵4-d Glucuronidation, hydroxylation, and oxidation of E1 (other than sulfation of E1).
↵4-e Division of the effective binding concentration of E1S by the extracellular protein concentration.
↵4-f Constrained as k multiplied by K .
↵4-g Unbound fraction of E1 in the extracellular medium.
↵4-h Obtained fromGarcı̀a-Ruiz et al. (1994).