Effect of intra-epididymal injection of copper particles on fertility, spermatogenesis, and tissue copper levels in rats

In male rats, a single injection of 10 mg metallic copper particles in oil into each caput epididymidis induced infertility, whilst leaving mating behaviour and blood testosterone levels unchanged. Fertility tended to recover 5.5 months after the copper treatment. Although the copper content of the caput epididymidis reached a level of around 100 times higher than control values, the serum copper concentration did not rise significantly. This finding and the observation that treated animals gained weight as fast as the controls suggest a low systemic toxicity of this method. The testicular copper concentration was significantly higher than that in controls and different degrees of damage, including vacuolation, karyorrhexis, pyknosis, and cytolysis, were seen mainly in pachytene spermatocytes and early spermatids. Clumps of foreign particles, apparently metallic copper, were found in the interstices of the caput epididymidis together with degenerative changes in the epithelial cells of the caput, suggesting a possible effect of copper on the epididymal epithelium. The viability of epididymal sperm decreased more markedly than the decrease in sperm density. It is therefore most likely that the major cause of infertility after copper injection into the caput epididymidis is a direct inhibitory effect of copper on the sperm, whilst damage to the seminiferous and epididymal epithelial may contribute.