In this study researchers investigated how intracellular NAD+ (iNAD) levels are regulated in several different types of healthy cells exposed to extracellular NAD+ (eNAD).They found eNAD+ more than doubled the quantity of iNAD+ in the cells through 3 preferred pathways.
- direct import across the cell membrane of intact NAD+
- conversion of NAD+ to NMN, then imported by the NMN transporter Slc12a8
- further conversion of NMN to NR, then imported by NRK1
- read more here