Toxicology of arsenate, arsenite, cadmium, lead, chromium, and nickel in testes of adult Swiss mice after chronic exposure by intraperitoneal route

Abstract

Background: Some residues such as the heavy metals cadmium (Cd), lead (Pb), chromium (Cr VI), nickel (Ni), and arsenic (As), this last one in its oxidized forms + 5 (arsenate) and + 3 (arsenite), can cause injuries to human health, so they are currently considered environmental health emergencies. In the testis, heavy metals can cause morphological and functional damage due to constant exposure acting chronically in individuals. Thus, we aimed to determine the toxicological mechanism of As⁺⁵, As⁺³, Cd, Cr VI, and Ni that leads to testicular damage and establish for the first time an order of toxicity among these studied heavy metals.

Methods: Forty-two Swiss mice at reproductive age (140 days) were used, randomly distributed into seven experimental groups (n = 6). Exposure to heavy metals was weekly performed, by intraperitoneal route. Group 1 received 0.7 mL 0.9% saline (control), and the other groups received 1.5 mg/ kg of As⁺⁵, As⁺³, Cd, Pb, Cr VI, or Ni, for six weeks.

Results: These studied heavy metals did not accumulate in the testis tissue. However, exposure to Ni induced moderate pathologies in the seminiferous tubules, plus changes in the tunica propria, blood vessels, lymphatic space, and carbonyl protein levels. Cd exposure caused moderate tubular histopathologies and changes in the blood vessels and lymphatic space. Cr VI induced slight tubular histopathologies, changes in the lymphatic space, blood vessels, and SOD activity. Pb and As⁺³ exposure triggered moderate tubular pathologies and changes in the SOD activity and carbonyl protein levels, respectively. Finally, As⁺⁵ induced only slight tubular pathologies.

Conclusion: The testicular histopathologies caused by the studied heavy metals are mainly triggered by changes in testicular oxidative balance. Based on our findings of histomorphological alterations, the toxicity order among the heavy metals is Ni>Cd>Cr(VI)>PbAs⁺³ >As⁺⁵. However, considering oxidative stress results, we propose the following testicular toxicity order for these heavy metals: Ni>As⁺³ > Cd>Cr(VI)>Pb>As⁺⁵. Ni exposure shows the most harmful among the heavy metals to the testis.

Keywords: Heavy metals; Male infertility; Spermatogenesis; Testicles; Toxicology.