| Summary: | 碩士 === 國立屏東科技大學 === 生物科技系所 === 102 === The contents of abstract in this thesis：
Many studies showed that environmental hormones exposure causes body malformations, intersex gonads and oxidative stress in organisms. Nonylphenol (NP) is used primarily as an additive in cleaning agents, and it is one of the environmental hormones. NP is often detected in rivers and drinking water. In our previous study has demonstrated that exposure low-concentration NP is enhanced oxidative stress in rat aorta. Additionally, there are some evidences showed that exposed to NP increases oxidative stress in the pancreas, and impairs insulin secretion function in pancreatic β-cell. However, in our daily life, we are exposure to many pollutants simultaneously, like NP, which may cause organisms dysfunctions. Therefore, we investigated that (1) whether long-term exposure to low dose of nonylphenol (NP) increases the multiple low-dose streptozotocin (STZ)-induced diabetic morbidity in rats, and (2) whether diabetes-induced macrovascular dysfunctions are exacerbated in the presence of low-dose nonylphenol (NP) exposure. Therefore, in this study, we were used 76 Sprague-Dawley male rats, divided in four groups: control (N=6), rat exposure to nonylphenol (NP, N=10), rat with streptozotocin-induced (STZ, N=30), rat exposure to nonylphenol and streptozotocin-induced group (NP+STZ, N=30) to explore these issues. Rats were tube-fed of nonylphenol 2mg/kg/day, for first 15 weeks, than we began to induced diabetic rats by intraperitoneal injection (i.p.) with streptozotocin (STZ, 20mg/kg), induction once for every two weeks, with period of eight weeks. The streptozotocin-induced rats were appeared symptoms of hyperglycemia, and measured the fasting blood glucose to assessment the diabetic morbidity in STZ and NP+STZ group. In the second stage, the considerable severity of hyperglycemia rats, which exposure to hyperglycemia for 11-14 weeks were chosen to assessed whether long-term exposure to low concentration of NP exacerbates the diabetes-induced vascular dysfunction. Then, we sacrificed rats, isolated the thoracic aorta to evaluate the vascular functions using phenylephrine(PE), a α1-receptor agonist, to measure the vasocontractile response, acetylcholine(NO-cyclic GMP pathway stimulator, 10-8-3x10-5M), clonidine (α2-adrenoceptor agonist stimulator,10-7-10-5M) or insulin(PI3K/Akt pathway stimulator, 1.6-9.6μM) to demonstrate the vasorelaxation response, and nitro-L-arginine methyl ester(L-NAME), a nitric oxide synthase inhibitor, to assess the basal nitric oxide(NO) release from endothelium. Also, we measured the basal reactive oxygen species (ROS) production and the NADPH-related oxidase activity indirectly in thoracic aorta, adipose and intestinal tissues by lucigenin-based chemiluminescence method. In the result, (1)The morbidity of diabetes in STZ group(morbidity: 79.3%) and NP+STZ group (morbidity: 80%) was similar, and the severity of hyperglycemia (STZ: 380±8mg/dL; NP+STZ: 380±9mg/dL) was also similar. In addition, the body weight of STZ group(505±3g) and NP+STZ group(528±4g) was also similar.(2)the basal endothelium-derived nitric oxide release in NP+STZ(30.4±1.6%) was significantly lower than that in STZ(36.4±1.1%) group, but the endothelium-dependent relaxation mediated by acetylcholine was no difference in these two groups；(3) however, the basal ROS production in aorta and adipose tissues was also significantly increased in NP+STZ group (aorta: 15.9±2.3 CPS/tissue(mg) ； adipose tissue: 11.7±0.9 CPS/tissue(mg)) than that in STZ group(aorta: 8.3±0.8 CPS/tissue(mg)；adipose tissue:7.2±0.9 cps/tissue(mg)), but not in the intestine tissues. In addition, the NADPH-related oxidase activity in aorta, adipose and intestine tissues was similar between STZ and NP+STZ group；(4)Finally, we also found that ,compared with the STZ group, the vasorelaxation mediated by clonidine (10-7~10-5M) was significantly decreased in NP+STZ group (from17.6±1.3% to 95.8±0.6%) than that in STZ group(from 27.1±2.0% to 97.4±0.6%). Also a similar situation was occurred in insulin-mediated (1.6~9.6μM) vasorelaxation (STZ：from 27.8±2.2% to 71.8±1.6%；NP+STZ: 16.6±1.6% to 64.2±2.3%). In conclusions, although long-term exposure to low concentration of NP did not increases other pollutants-induced diabetic morbidity. But it was exacerbates the diabetic-induced macrovascular endothelium dysfunction, such as decreases the activity of nitric oxide bioavailability and increases oxidative stress in tissues. Therefore, we suggest that diabetic patients should avoid exposure to the environmental hormones, even just in the low concentrations, it could exacerbates the diabetic- induced macrovascular dysfunctions.
Key words: endocrine disrupting chemicals, nonylphenol, macrovascular dysfunction, diabetes mellitus.
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