Effect of Basolateral HSA on MDZ First-Pass ER
| Treatment | Incubation Time1-a | Intracellular MDZ | Rate of 1′-OH MDZ Formation | Basolateral MDZ | ER1-b |
|---|---|---|---|---|---|
| min | pmol/culture | pmol/min/culture | % dose | ||
| Control | 20 | 389 ± 8.5 | 2.9 ± 0.08 | 8.9 ± 0.3 | 13.3 ± 0.1 |
| 5% FBS | 20 | 333 ± 9.51-c | 3.2 ± 0.43 | 11.7 ± 1.4 | 11.5 ± 2.4 |
| 4 g/dl HSA | 10 | 225 ± 301-c | 2.3 ± 0.44 | 9.9 ± 1.5 | 5.2 ± 1.01-d |
Caco-2 monolayers were dosed apically with 3 μM MDZ. Both MDZ and 1′-OH MDZ were measured in the apical and basolateral media and in the cell homogenate collected at the indicated time. Each value represents the mean (and S.D.) of three cultures.
↵1-a The incubation time was selected to maintain sink conditions where <10% of the apical dose had crossed into the basolateral compartment.
↵1-b The first-pass ER was calculated by application of the total amount of 1′-OH MDZ formed, and total MDZ in the basolateral medium, to eq. 3.
↵1-c There was a statistically significant difference in the mean cell MDZ content for control cultures and cultures treated with basolateral FBS (p = .026) or HSA (p < .001).
↵1-d There was a significant difference in the mean ER for cultures treated with basolateral HSA compared with control (p = .002).