Carrier-mediated uptake of the endogenous cannabinoid anandamide in RBL-2H3 cells

Anandamide (N-arachidonylethanolamide) is an endogenous cannabinoid that mi mics the pharmacologic effects of Delta(9)-tetrahydrocannabinol, the major bioactive substance in marijuana. Anandamide appears to be synthesized, rel eased, and inactivated by mechanisms similar to those for other neurotransm itters. Of interest to the present studies are reports that anandamide unde rgoes carrier-mediated uptake into neuronal or glial cells after release, f ollowed by rapid intracellular degradation by the intracellular fatty acid amidohydrolase. In addition to effects in the brain, anandamide has multipl e effects in the periphery, particularly on cells of the immune system that express both a peripheral cannabinoid receptor and amidohydrolase enzyme. We have performed a detailed characterization of anandamide uptake in the c ognate mast cell line RBL-2H3 to test the hypothesis that the uptake system in peripheral cells is also carrier-mediated and functionally similar to t hat observed in the central nervous system. RBL-2H3 cells exhibited robust, saturable transport of [H-3]anandamide that was both time-and temperature- sensitive. This transport activity was not dependent on extracellular ion g radients for uptake and was inhibited selectively by other fatty acid-deriv ed molecules, anandamide congeners, and the psychoactive cannabinoids such as Delta(9)-tetrahydrocannabinol. We conclude that anandamide transport in the RBL-2H3 cells is carrier-mediated, and uptake in peripheral cells is fu nctionally and pharmacologically identical with that observed in neurons an d astrocytes.