LAUSR

ABSTRACT Compounds extracted from the cannabis plant, including the psychoactive &Dgr;9‐tetrahydrocannabinol (THC) and related phytocannabinoids, evoke multiple diverse biological actions as ligands of the G protein‐coupled cannabinoid receptors CB1 and CB2. In addition, there is increasing evidence that phytocannabinoids also have non‐CB targets, including several ion channels of the transient receptor potential superfamily. We investigated the effects of six non‐THC phytocannabinoids on the epithelial calcium channels TRPV5 and TRPV6, and found that one of them, &Dgr;9‐tetrahydrocannabivarin (THCV), exerted a strong and concentration‐dependent inhibitory effect on mammalian TRPV5 and TRPV6 and on the single zebrafish orthologue drTRPV5/6. Moreover, THCV attenuated the drTRPV5/6‐dependent ossification in zebrafish embryos in vivo. Oppositely, 11‐hydroxy‐THCV (THCV−OH), a product of THCV metabolism in mammals, stimulated drTRPV5/6‐mediated Ca2+ uptake and ossification. These results identify the epithelial calcium channels TRPV5 and TRPV6 as novel targets of phytocannabinoids, and suggest that THCV‐containing products may modulate TRPV5‐ and TRPV6‐dependent epithelial calcium transport.