Cannabinoids inhibit the respiration of human sperm.

Objective: To investigate the effects of the psychotropic compounds Delta(9)-tetrahydrocannabinol (Delta(9)-THC) and Delta(8)-tetrahydrocannabinol (Delta(8)-THC) on sperm mitochondrial O(2) consumption (respiration).

Setting: State University of New York Upstate Medical University, Syracuse, New York.

Patient(s): Forty-one men who visited the andrology laboratory for fertility evaluation.

Intervention(s): None.

Main Outcome Measure(s): A phosphorescence analyzer that measures O(2) concentration in sperm suspensions as a function of time was used to measure respiration.

Result(s): An immediate decline in the rate of respiration was observed when Delta(9)-THC or Delta(8)-THC was added to washed sperm. The inhibition was concentration dependent, and Delta(9)-THC was the more potent of the two compounds. Respiration was much less affected when Delta(9)-THC or Delta(8)-THC was added to neat semen, suggesting the presence of protective factors in seminal plasma. Both compounds inhibited the respiration of isolated mitochondria, illustrating that direct mitochondrial damage is likely the primary mechanism of action.

Conclusion(s): The two main active cannabinoids of the marijuana plant, Delta(9)- and Delta(8)-THC, are potent inhibitors of mitochondrial O(2) consumption in human sperm. These findings emphasize the adverse effects of these toxins on male fertility. The cytoprotective capacity of seminal plasma deserves further investigation.