Objectives: Our previous study suggested that adrenaline (epinephrine) could be an effective absorption enhancer for ginsenoside Rg1 (Rg1). This study focused on the transport mechanism of Rg1 and the role of sodium-dependent glucose co-transporter 1 in the regulation of Rg1 uptake after exposure to adrenaline.
Methods: Caco-2 cells were used as an in-vitro model to assess the absorption mechanism of Rg1. Also the effect of D-glucose on adrenaline-induced absorption of Rg1 was investigated in vivo in rats.
Key findings: Results showed that the uptake of Rg1 was temperature-dependent. The transport from the basolateral side to the apical side was significantly lower compared with that from the apical to the basolateral side (P < 0.01). The transport of Rg1 was concentration dependent (Km was 41.60 mM, V(max) was 353.75 mol/cm(2)/min). Cells incubated with D-glucose-free medium exhibited significantly greater Rg1 uptake (+ 62.6%) compared with cells in D-glucose-containing medium. The data indicated that sodium-dependent glucose co-transporter 1 was involved in the transport of Rg1. Adrenaline-induced uptake of Rg1 was significantly inhibited in the presence of phlorizin and the absence of Na+. In the in-vivo study in rats, it was found that after co-administration with D-glucose, the adrenaline-induced absorption of Rg1 was inhibited. The area under the concentration-time curve (AUC(0 --> infinity)) value was significantly decreased from 64.57 +/- 27.08 to 1.37 +/- 0.42 microg/ml h (P < 0.001).
Conclusions: The data suggested that adrenaline enhanced the absorption of Rg1 by regulating sodium-dependent glucose co-transporter 1.