Modulation of P-glycoprotein function by amlodipine derivatives in brain microvessel endothelial cells of rats1

Abstract

Aim: To investigate whether the amlodipine derivatives, CJX1 and CJX2, have a modulative effect on P‐glycoprotein (P‐gp) function in rat brain microvessel endothelial cells (RBMEC). Methods: Isolated RBMEC were cultured in DMEM/F12 (1:1) medium. The amount of intracellular rhodamine (Rh123) was determined, using a fluorescence spectrophotometer, to evaluate the function of P‐gp. Results: The accumulation of Rh123 in RBMEC was potentiated in a concentration dependent manner after incubation with CJX1 and CJX2 at 1, 2.5, 5, and 10 μmol/L (P<0.01), but no accumulation of Rh123 was observed in human umbilical vein endothelial cells after incubation with CJX1 and CJX2 10 μmol/L (P>0.05). Accumulation of intracellular Rh123 was increased and efflux of intracellular Rh123 was decreased in a time‐dependent manner from 0–100 min after CJX1 and CXJ2 at 10 μmol/L treatment. The inhibitory effect of CJX1 and CJX2 on P‐gp function was reversible and remained even at 120 min after removal of CJX1 and CJX2 at 2.5 μmol/L from the medium. Conclusion: CJX1 and CJX2 exhibited a potent effect in the inhibition of P‐gp function in vitro.

Polarized P-glycoprotein expression by the immortalised human brain endothelial cell line, hCMEC/D3, restricts apical-to-basolateral permeability to rhodamine 123

“…The t 1/2 obtained here for rh123 efflux (~13 min) is in agreement with another study that found a t 1/2 of similar magnitude in rat primary BECs (~ 10 min) (Ji et al, 2005). However, in contrast to the relatively modest increase in the efflux t 1/2 caused by another competitive inhibitor, verapamil, in that study (t 1/2 ~ 20 min), in the present study vinblastine caused a much more potent inhibition (t 1/2 ~ 110 min).…”

Reversion of Multidrug Resistance in a Chemoresistant Human Breast Cancer Cell Line by β-Elemene

“…Rhodamine 123 (Rh123) is a fluorescent dye that could be used as a function assay for P-gp [18,19]. Cells were seeded into 6- well plates at a density of 1 × 10 6 per well.…”

CJZ3, a lomerizine derivative, modulates P-glycoprotein function in rat brain microvessel endothelial cells1

“…Similar results for CJZ3 have been observed in doxorubicinresistant human myelogenous leukemia (K562/DOX) cells (unpublished data). We also found that the ability of CJZ3 to cause the accumulation of Rh123 was greater than that of CJX1 and CJX2, the amlodipine derivatives studied previously [17] : the rate constant of uptake (K uptake ) was higher in 10 µmol/L CJZ3-treated cells (0.060) than in CJX1-treated cells (0.0508) and in CJX2-treated cells (0.0495), and the rate constant of efflux (K efflux ) was lower (0.0068) than in CJX1-treated cells (0.0097) and in CJX2-treated cells (0.0127), suggesting that CJZ3 also has a more potent inhibitory effect on P-gp function than CJX1 and CJX2.…”