Carrier‐mediated transport and enzymatic hydrolysis of the endogenous cannabinoid 2‐arachidonylglycerol

The human astrocytoma cell line CCF-STTG1 accumulates [H]2-AG through an Na‡and energy-independent process, with a Km of 0.7 0.1 ìM. Non-radioactive 2-AG, anandamide or the anandamide transport inhibitor 4-hydroxyphenyl arachidonamide inhibit [H]2-AG uptake with half-maximal inhibitory concentrations (IC50) of 5.5 1.0 ìM, 4.2 0.3 ìM and 1.8 0.1 ìM, respectively. A variety of lipid transport substrates and inhibitors interfere with neither [H]2-AG nor [H]anandamide uptake. These results suggest that 2-AG and anandamide are internalized in astrocytoma cells through a common carrier-mediated mechanism. After incubation with [H]2-AG, radioactivity is recovered in phospholipids, monoacylglycerols (unmetabolized [H]2-AG), free fatty acids ([H]arachidonate) and, to a minor extent, diacylglycerols and triacylglycerols. Arachidonic acid (100 ìM) and triacsin C (10 ìM), an acyl-CoA synthetase inhibitor, prevent incorporation of [H]arachidonic acid in phospholipids and signi®cantly reduce [H]2-AG transport. Thus, the driving force for 2-AG internalization may derive from the hydrolysis of 2-AG to arachidonate and the subsequent incorporation of this fatty acid into phospholipids. NeuroReport 11:1231±1235 & 2000 Lippincott Williams & Wilkins.