Investigation of the relationship between heavy metal levels and several reproductive characteristics, oxidative stress and testicular apoptosis in rams grown around thermal power plants

In this study, it was aimed to investigate the changes in heavy metal levels in serum and testicular tissue, and serum steroid hormone levels, epididymal spermatological characteristics, tissue oxidative stress markers, testicular histology and testicular apoptosis level in rams raised in remote and near regions of the thermal power plant. For this purpose, a total of 75, 12-15 months old, Akkaraman rams, which were born and grown in regions far from [250 km radius distance, Group 1 (control), n = 25], near at medium level (20 km radius distance, Group 2, n = 25) and the nearest (10 km radius distance, Group 3, n = 25) to Afşin-Elbistan Thermal Power Plant, were used. The blood along with testis and epididymis tissues were taken from the animals brought to the abattoir for slaughter. Heavy metal levels in the blood and testicles; testosterone, estradiol and DHEAS levels in serum; testicular and cauda epididymal oxidative stress levels; cauda epididymal spermatological parameters; testicular histopathological and apoptotic changes were examined. Serum Cd, Hg and Pb levels remained below the minimum detectable value in all groups. Serum Al, Cr, As, Ag and Sn levels of animals in Groups 2 and 3 were significantly higher than Group 1 (P <0.01; P <0.001). Serum Cu levels of Group 1 were observed being higher than the other groups (P <0.001). The testicular tissue levels of Al, V, Ni, Ag and Cd (P <0.05; P <0.001) in Groups 2 and 3 were higher than Group 1. Testicular Cr, As and Pb levels were found significantly higher only in Group 3 (P <0.01; P <0.001). While testicular tissue Hg level remained below the minimum detectable value in Groups 1 and 2, it was determined as 430.83±156.15 ppb in Group 3. Testicular Cu and Zn levels were significantly lower in Groups 2 and 3 compared to Group 1 (P <0.01; P <0.001). Serum DHEAS levels were below the minimum detectable value in all groups. The lowest serum testosterone level was determined in Group 3. Compared to Group 1, the significantly higher testicular (P <0.01) and cauda epididymal (P <0.05) MDA level was determined in Group 3, whereas the significantly lower GPx level in the same tissues was found in Group 3 ( P <0.05; P <0.001). In terms of testicular tissue CAT activities, a statistical decrease was observed in Groups 2 and 3 compared to Group 1 (P <0.001). Compared to Group 1, there was a statistical decrease (P <0.001) in Group 3 in terms of spermatozoon density and a statistical increase (P <0.01) in Groups 2 and 3 with regard to dead spermatozoon ratio. Histopathologically, it was determined that there was a decrease in DST and GCLT (P <0.001), arrest in spermatogenesis in some tubules in Groups 2 and 3, multi-core syncytial cell formations, which are an indicator of hypoplasia, especially in Group 3. On the other hand, compared to Group 1, there was a statistically significant increase in Bax apoptotic protein expression level and Bax/Bcl-2 ratio in Group 3 (P <0.05). As a result, it was concluded that the endocrine and exocrine reproductive potentials of rams born and grown in region close to the thermal power plant were clearly damaged due to heavy metal accumulations in their testicular tissues.