The transport mechanism of monocarboxylate transporter on spinosin in Caco-2 cells

Objectives: The aim of this study was to determine the uptake mechanism of spinosin (SPI) by the monocarboxylic acid transporters (MCTs) in Caco-2 cells. Methods: The Caco-2 cells were pretreated with various monocarboxylic acids, and the uptake of spinosin from Caco-2 cells was measured by High Performance Liquid Chromatography (HPLC). Key findings: Preloading of various monocarboxylic acids enhanced the uptake of SPI, especially salicylic acid (a substrate of MCTs) had a 23.4 times increase in SPI uptake, indicating that the monocarboxylic acid transporters had an efflux effect on SPI uptake and salicylic acid had a strong inhibition on SPI efflux in Caco-2 cells. At the same time, the uptake of SPI through Caco-2 cells was Na+- and temperature-dependent, pretreatment without Na+ significantly increased the uptake of SPI by 1.85 times and incubated at low temperature (4 °C) SPI uptake increased 20% than that of 37 °C. Furthermore, SPI was transported mainly via a carrier-mediated transport: [Vmax = 5.364 μg/mg protein, Km = 657.0 μg/mL]. Conclusion: The uptake of spinosin (SPI) in Caco-2 cells was mainly regulated by the monocarboxylic acid transporters along with Salicylic acid.