Transport of endocannabinoids across the plasma membrane and within the cell.

Endocannabinoids are readily accumulated from the extracellular space by cells. Although their uptake properties have the appearance of a process of facilitated diffusion, it is by no means clear as to whether there is a plasma membrane transporter dedicated to this task. Intracellular carrier proteins that shuttle the endocannabinoid anandamide from the plasma membrane to its intracellular targets such as the metabolic enzyme, fatty acid amide hydrolase, have been identified. These include proteins with other primary functions, such as fatty-acid-binding proteins and heat shock protein 70, and possibly a fatty acid amide hydrolase-like anandamide transporter protein. Thus, anandamide uptake can be adequately described as a diffusion process across the plasma membrane followed by intracellular carrier-mediated transport to effector molecules, catabolic enzymes and sequestration sites, although it is recognized that different cells are likely to utilize different mechanisms of endocannabinoid transport depending upon the utility of the endocannabinoid for the cell in question.