Zralý Z, Bendová J, Svecová D, Faldíková L, Vĕzník Z, Zajícová A
Veterinary Research Institute, Brno, Czech Republic.
Vet Med (Praha). 1997 Dec;42(12):345-54.
Effects of oral intake of nitrates on selected biochemical and endocrinological indices and its impact on reproductive functions were investigated in five feeder bulls aged 16-18 months. The bulls were tested prior to (30 days), during (30 days) and after (35 days) the period of the nitrate administration. The initial dose of 100 g potassium nitrate per day was increased at weekly intervals by 50 g up to 250 g per day. The administration of nitrates resulted in a highly significant (P < 0.01) increase in methaemoglobin concentration and a non-significant decrease in the concentration of beta-carotene and a highly significant (P < 0.01) decrease in the concentration of E vitamin in blood serum. A significant (P < 0.01) increase in blood serum concentration of bile acids and prolonged biological half-life of progesterone were suggestive of an impairment of liver metabolism. Prolonged intake of excessive doses of nitrates resulted in a significant (P < 0.05) increase in cortisol concentration during and after the administration period, while depressed thyroid gland activity was evident from a significant (P < 0.05) decrease in thyroxin concentration during the administration period. A suppression of hypothalamic functions after the administration period was documented by non-detectable levels (< 0.001 microgram/ml) of thyrotropin in TRH test. Depressive effects of nitrates on the function of Leydig cells during and particularly after the administration period were apparent from weakening testicular responses to a treatment with GnRH. Biochemical analyses of seminal plasma revealed a highly significant (P < 0.01) increase in total acid phosphatase activity and a significant (P < 0.05) decrease in the concentration of fructose. No other significant changes in seminal plasma components were observed. Adverse effects of excessive intake of nitrates were also evident from reduced sperm motility in the 120-min thermal test. While no difference was found in the frequency of primary morphological abnormalities, the number of secondary abnormalities rose by 115% in the post-administration period and was suggestive of damaged membrane integrity. Histological examinations revealed degenerative lesions in cells of the spermiocyte and spermatid layers.
研究了口服硝酸盐对5头16 - 18月龄育肥牛某些生化和内分泌指标的影响及其对生殖功能的作用。在硝酸盐给药前（30天）、给药期间（30天）和给药后（35天）对公牛进行检测。初始剂量为每天100克硝酸钾，每周增加50克，直至每天250克。硝酸盐给药导致高铁血红蛋白浓度显著升高（P < 0.01），β-胡萝卜素浓度无显著下降，血清中维生素E浓度显著降低（P < 0.01）。血清胆汁酸浓度显著升高（P < 0.01）以及孕酮生物半衰期延长提示肝脏代谢受损。长期摄入过量硝酸盐导致给药期间及给药后皮质醇浓度显著升高（P < 0.05），而给药期间甲状腺素浓度显著降低（P < 0.05）表明甲状腺活动受到抑制。在促甲状腺激素释放激素（TRH）试验中促甲状腺激素水平未检测到（< 0.001微克/毫升），证明给药后下丘脑功能受到抑制。从睾丸对促性腺激素释放激素（GnRH）治疗反应减弱可明显看出，硝酸盐在给药期间尤其是给药后对睾丸间质细胞功能有抑制作用。精浆生化分析显示总酸性磷酸酶活性显著升高（P < 0.01），果糖浓度显著降低（P < 0.05）。未观察到精浆成分有其他显著变化。在120分钟热试验中精子活力降低也明显显示出过量摄入硝酸盐的不良影响。虽然在初级形态异常频率上未发现差异，但给药后次级异常数量增加了115%，提示膜完整性受损。组织学检查显示精母细胞和精子细胞层细胞有退行性病变。
