Cannabinoids reduce fertility of sea urchin sperm

Abstract

Cannabinoids are potent pharmacological substances derived from marihuana. The effects of Δ9-tetrahydrocannabinol (THC), cannabinol (CBN), and cannabidiol (CBD) on fertilization in the sea urchin Strongylocentrotus purpuratus were investigated. Insemination of THC-treated eggs (5–400 μM) with excess sperm did not result in polyspermic fertilization. At minimal sperm densities, THC (0.1–10 μM) inhibited fertilization in a dose-dependent manner. Pretreatment of eggs with THC did not reduce their receptivity to sperm. Pretreatment of sperm with THC reduced their fertilizing capacity. The concentration of THC required to reduce sperm fertility by 50% was 1.1 ± 1.1 μM. The fertilizing capacity of THC-treated sperm depended on concentration of sperm and duration of pretreatment. The fertility of sperm at minimal densities was reduced by 50% at 129.3 ± 43 s treatment with 10 μM THC. The adverse effect of THC on sperm fertility was reversible. CBN and CBD at comparable concentrations (0.1–10 μM) inhibited fertilization in a manner similar to THC. First division was not delayed in zygotes that were fertilized with sperm pretreated with 10 μM THC. These studies show that cannabinoids directly affect the process of fertilization in sea urchins by reducing the fertilizing capacity of sperm.