THE MECHANISM OF AGE-RELATED CHANGES IN THE RELEASE OF NITRIC OXIDE.

冠状动脉疾病引起的心血管疾病的发病率随着年龄的增长而增加。内皮素在调节血管张力和维持心血管功能中起重要作用。我们以前的研究表明，几种缩血管肽如血管紧张素II和内皮素-1刺激年轻大鼠冠状动脉中NO的释放，但在老年大鼠的生产减弱。这种受损的NO生产可能有助于更大的血管收缩剂在老年大鼠的收缩作用。而血管收缩剂对老年大鼠PGI_2释放的刺激作用则明显大于青年大鼠。为了阐明NO和PGI_2释放的增龄性变化的机制，我们检测了与年龄相关的负责合成NO和PGI_2的酶及其受体表达的变化，以揭示PGI_2产生的调节机制。从3月龄和27月龄Fischer 344大鼠中分离主动脉和心脏。在37℃下以75cmH_2O恒压灌注心脏。用流量计测量冠状动脉流量的变化。采用酶免疫法（EIA）检测冠脉流出液中6-keto-PGF <1α>的含量，实时荧光定量PCR和Western blot检测冠脉流出液中PGI 2受体、NO、PGI合成酶和环氧合酶1（考克斯-1）的表达。老年大鼠排出液中PGI_2的释放量大于青年大鼠。PGI_2受体含量无年龄差异。考克斯-1和前列环素合成酶在老年大鼠的表达增加。老年大鼠冠状动脉中考克斯-1和PGI合成酶的表达增加可能与PGI_2的生成增加有关。NO合成酶和精氨酸转运体的表达是否随增龄而变化尚不清楚。

The incidence of cardiovascular disorder due to coronary artery disease increases with advansing age. Endothelium plays an important role in regulating vascular tone and in maintaining the cardiovascular function. We previously demonstrated that several vasoconstricting peptides such as angiotensin II and endothelin-1 stimulated the release of NO in the coronary artery of young rat, but the production was attenuated in the aged rat. This impaired production of NO may contribute to the greater constrictor effect of the vasoconstrictors in the aged rat. In contrast, the vasoconstrictors stimulated the release of PGI_2 to a much greater extent in aged rats than in young rats. It might be possible that aged endothelial cells could produce PGI_2 as a compensation-mechanism for reduced production of NO.To elucidate the mechanism of age-related changes in the release of NO and PGI_2, We examined the age-related changes in the expression of enzymes responsible for the synthesis of NO and PGI_2 and PGI_2 receptors to reveal the mechanism of regulation of PGI_2 production. Aorta and hearts were isolated from 3- and 27- months old Fischer 344 rats. Hearts were perfused with constant pressure (75 cmH_2O) at 37℃. Changes in the coronary flow were measured with a flow meter. 6-keto-PGF_<1α> in the coronary effluent was measured with EIA.Changes in the expression of PGI_2 receptors, NO and PGI synthase and cyclooxygenase-1 (COX-1) were quantified by real-time PCR and Western blot analysis. Release of PGI_2 into the effluent was greater in the aged rat than young rat. There was no age-related difference in the amount of PGI_2 receptor. Expression of COX-1 and PGI synthase was increased in the aged rat. These increases in COX-1 and PGI synthase may be responsible for the increased production of PGI_2 in the aged rat coronary artery. It is not yet clarified whether the expressions of NO syntase and arginine transportor change with aging.