Effects of Δ8-Tetrahydrocannabinol, Δ9-Tetrahydrocannabinol, and Crude Marihuana on Human Cells in Tissue Culture

In recent years a moderate controversy has arisen with respect to the possible cytotoxic effects of marihuana and its related compounds. Neu et al. [6] studied Δ9-tetrahydrocannabinol (Δ9-THC) in in vitro experiments with human leukocytes and found no increase in chromosome abnormalities. Stenchever and Allen [9] demonstrated similar negative findings in an experiment in which the Δ9-THC was placed in tissue culture media after phytohemag-glutinin had been added to the leukocytes. In these experiments the Δ9-THC was present throughout the entire 72 hr of culture, and a number of concentrations ranging from 0.1–100 µg/cc of culture medium were studied. At the higher concentrations, there was a noticeable increase in cell death and decreased mitotic activity. Pace et al. similarly could find no chromosome damage in rat cells after exposure to marihuana resins [8]. Martin and coworkers [4] exposed both embryonic rat fibroblasts and human leukocytes to cannabis resins in vitro in separate studies and demonstrated a dose-related decrease in mitotic rate but no increase in chromosome abnormalities.